In this criminal case, the trial court denied defendant’s pretrial motion to suppress evidence seized during a warrantless search of defendant’s apartment following his arrest. On appeal from defendant’s subsequent conviction, the Court of Appeals reversed and remanded for a new trial, holding that “[djefendant’s consent to the search was obtained by exploitation of illegal police conduct” and that, therefore, the motion to suppress should have been granted. State v. Rodriguez, 110 Or App 544, 551, 823 P2d 1026 (1992). We conclude that defendant’s consent was not obtained by exploitation of any illegal police conduct. Consequently, we reverse the decision of the Court of Appeals and reinstate the judgment of the circuit court.
Defendant is an alien who had been convicted of possession of a controlled substance. As a result, he was subject to deportation. 8 USC § 1251(11) (1988). A special agent with the United States Immigration and Naturalization Service (INS) learned of defendant’s conviction and sought to arrest him pending deportation proceedings.1 The INS agent obtained an administrative arrest warrant by presenting a certified copy of defendant’s record of conviction to the INS Assistant District Director for Investigations in Portland.2 After obtaining the warrant, the INS agent went to defendant’s apartment to make the arrest, accompanied by six Portland police officers and an FBI agent who were members of a regional organized crime narcotics task force.
At the hearing on the motion to suppress, the INS agent described defendant’s arrest at his apartment as follows:
“Q [DISTRICT ATTORNEY:] What happened when you got there?
“A [AGENT:] Well, we arrived there and I knocked on the door and [defendant] appeared at the window and opened the door up. I showed him my credentials, speaking Spanish *30identified myself as an immigration officer, I showed him a copy of the warrant, and told him that I had a warrant for his arrest and that he was under arrest.
“Q Was that still through the window?
“A No, he had opened the door. It was in the doorway.
“Q Okay. And what did you ask him at that point? Did you read him his Miranda rights?
“A Yes. Yeah, the door was open, as I say. We were more or less — I was by myself. The rest of the unit wasn’t there, they were off to the side. And as I told him — identified myself and showed him a copy of the warrant and so forth, and my badge, he said, ‘Okay. ’ He submitted peacefully to the arrest. He says, ‘Okay,’ and he stepped back in which was an indication to me to step in and I was going to do what I had to for him to be arrested.
“And I stepped in and I read him Miranda rights from DEA form 13A in Spanish. I read his rights. He said he understood them.
“And then I asked him, ‘Do you have any drugs or guns in the house?’ And he said, ‘No, go ahead and look.’ And I said, ‘Can we search?’ You know, ‘Want to consent to search,’ and so forth. And he said, ‘Yes, go ahead.’
“And then the other team members came in and we searched the apartment.”
During the search, one of the Portland police officers found a gun under a pillow, and the FBI agent found another gun in a closet. In response to questioning by the INS agent, defendant stated that one of the guns was his and that, although the other gun was not his, it would have his fingerprints on it.
Defendant was charged with two counts of being an ex-convict in possession of a firearm, ORS 166.270 (1987).3 Before trial, he moved to suppress both the guns and his statements.4 He argued that the administrative arrest warrant was not supported by oath or affirmation, as required by *31the Oregon and United States Constitutions,5 that the arrest was therefore unlawful, and that the guns and statements should be suppressed as the “fruit” of the unlawful arrest. Defendant also argued that the Portland police had participated in the arrest in violation of ORS 181.850(1), set out infra, and that the evidence should be suppressed as the “fruit” of that alleged illegality. The trial court denied the motion to suppress, and defendant was convicted.
On appeal from that conviction, the Court of Appeals concluded that defendant’s arrest was unlawful, because the arrest warrant was not valid under Article I, section 9, of the Oregon Constitution, and because the arrest was not a valid warrantless arrest. State v. Rodriguez, supra, 110 Or App at 548-50. The court then concluded that “[defendant's consent to the search was obtained by exploitation of illegal police conduct.” Id. at 551. Consequently, the court reversed and remanded for a new trial. Id.6 We allowed the state’s petition for review to address several issues of constitutional import presented by this case.
SUB-CONSTITUTIONAL ANALYSIS
Before addressing defendant’s constitutional claims, we address defendant’s sole sub-constitutional argument. See State v. Lajoie, 316 Or 63, 66, 849 P2d 479 (1993) (applying this court’s customary methodology). Defendant argues that suppression of the gun discovered by the Portland police officer was required, because the Portland police participated in his arrest in violation of ORS 181.850(1). That statute provides:
“No law enforcement agency of the State of Oregon or any political subdivision of the state shall use agency moneys, equipment or personnel for the purpose of detecting *32or apprehending persons whose only violation of law is that they are persons of foreign citizenship residing in the United States in violation of federal immigration laws.”
We reject defendant’s argument for two reasons. First, the Portland police officers did not violate ORS 181.850(1) by participating in defendant’s arrest, because they were not there “for the purpose of detecting or apprehending” defendant. On the contrary, the trial court expressly found that “[t]hey were looking for violations ofthe state statutes.” Nothing in ORS 181.850(1) prohibits state officers whose purpose is to determine whether any state law has been violated from accompanying a federal officer on an arrest such as the one that occurred in this case.
Second, even assuming that the Portland police officers were present, at least in part, “for the purpose of * * * apprehending” defendant, and further assuming that being present with such mixed motives would be a violation of ORS 181.850(1), defendant has failed to demonstrate that suppression of evidence is a necessary consequence of such a violation. See, e.g., State v. Trenary, 316 Or 172, 850 P2d 356 (1993) (failure of police officer to inform driver of consequences of refusing field sobriety test did not require suppression of test results); State v. Valentine/Darroch, 264 Or 54, 504 P2d 84 (1972) (evidence obtained in violation of Oregon “knock and announce” statute not subject to suppression), cert den 412 US 948 (1973). Defendant’s sub-constitutional argument is not well taken.
STATE CONSTITUTIONAL ANALYSIS
We proceed to defendant’s constitutional arguments. At trial, on appeal, and on review, defendant has invoked his rights under both the Oregon and United States Constitutions. Before addressing defendant’s claims under the federal constitution, we address defendant’s claims under the state constitution. Sterling v. Cupp, 290 Or 611, 614, 625 P2d 123 (1981). In this case, the applicable provision of the Oregon Constitution is Article I, section 9, which provides:
“No law shall violate the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable search, or seizure; and no warrant shall issue but upon probable cause, supported by oath or affirmation, and *33particularly describing the place to be searched and the person or thing to be seized.”
A defendant’s right under Article I, section 9, to be “secure * * * against unreasonable search, or seizure” is vindicated through the sanction of suppression of evidence. State v. Davis, 313 Or 246, 253, 834 P2d 1008 (1992). As this court stated in Davis, “if that constitutional right to be ‘secure’ against impermissible government conduct is to be effective, it must mean that the government cannot obtain a criminal conviction through the use of evidence obtained in violation of a defendant’s rights under that provision.” Ibid. Therefore, to determine whether defendant was entitled to suppression of the guns in this case, we must determine whether those guns were “obtained in violation” of defendant’s right against unreasonable search or seizure under Article I, section 9.
Defendant premised his motion to suppress on the argument that the administrative arrest warrant used to secure his arrest violated Article I, section 9, because it was not “supported by oath or affirmation,” as required by that provision. The state has conceded that the arrest warrant did not satisfy the oath or affirmation requirement of Article I, section 9.7 The state denies, however, that suppression of the guns is required as a result of that concession. The state advances three arguments for sustaining the trial court’s decision not to suppress the guns in this case.
First, the state argues that, despite the failure of the warrant to comply with Article I, section 9, defendant’s arrest was not an “unreasonable” seizure under that provision, because the Oregon Constitution cannot confer a right to be secure against seizure by a federal agent executing a federal warrant that is valid under federal law. Second, the state *34argues that, even if the Oregon Constitution could confer such a right, defendant’s arrest was not an “unreasonable” seizure under Article I, section 9, because it was a permissible warrantless arrest based on probable cause. Finally, the state argues that, even if defendant’s arrest was an “unreasonable” seizure under Article I, section 9, suppression of the guns was not required, because defendant consented voluntarily to the search that uncovered the guns, and the unlawfulness of the arrest did not invalidate that consent. We shall address each of those arguments in turn.
Applicability of the Oregon Constitution
The state first contends that, because the arresting officer was a federal agent executing a federal warrant that was valid under federal law, defendant’s arrest could not have violated any right of defendant under the Oregon Constitution. As the basis for that argument, the state relies on the Supremacy Clause (Article VI, paragraph 2) of the Constitution of the United States, which provides:
“This Constitution, and the Laws of the United States which shall he made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall he the supreme Law of the Land; and the Judges in every State shall he bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding. ’ ’
According to the state, the Supremacy Clause prevents the State of Oregon from conferring on any person a right to be secure against such a seizure as occurred in this case.
We will assume, without deciding (at this point), that the administrative warrant for defendant’s arrest was valid under federal law.8 Even with that assumption, however, we reject the staters contention that the Supremacy Clause renders Article I, section 9, inapplicable to the arrest in this case.
*35In State v. Davis, supra, this court recognized the broad protection granted to individuals under Article I, section 9, in relation to criminal prosecutions in this state:
“If the government seeks to rely on evidence in an Oregon criminal prosecution, that evidence must have been obtained in a manner that comports with the protections given to the individual by Article I, section 9, of the Oregon Constitution. It does not matter where that evidence was obtained (in-state or out-of-state), or what governmental entity (local, state, federal, or out-of-state) obtained it; the constitutionally significant fact is that the Oregon government seeks to use the evidence in an Oregon criminal prosecution. Where that is true, the Oregon constitutional protections apply.”
313 Or at 254. It is true that Davis itself did not involve conduct by a federal officer acting under the authority of federal law, as does the present case. However, the wording just quoted specifically covers the facts presented here. We see no reason why the factual distinction between a state officer and a federal officer has any legal significance in determining whether certain evidence is admissible in an Oregon criminal prosecution. The rule announced in Davis applies to the arrest that occurred in this case.
The Supreme Court of the United States has described the preemptive effect of the Supremacy Clause as follows:
“The Supremacy Clause of Art VI of the Constitution provides Congress with the power to pre-empt state law. Preemption occurs when Congress, in enacting a federal statute, expresses a clear intent to pre-empt state law, * * * when there is outright or actual conflict between federal and state, law, * * * where compliance with both federal and state law is in effect physically impossible, * * * where there is implicit in federal law a barrier to state regulation, * * * where Congress has legislated comprehensively, thus occupying an entire field of regulation and leaving no room for the States to supplement federal law, * * * or where the state law stands as an obstacle to the accomplishment and execution of the full objectives of Congress.”
Lousiana Public Service Comm. v. FCC, 476 US 355, 368-69, 106 S Ct 1890, 90 L Ed 2d 369 (1986). According to the Court, “[t]he underlying rationale of the pre-emption doctrine, as stated more than a century and a half ago, is that the *36Supremacy Clause invalidates state laws that ‘interfere with or are contrary to, the laws of congress.’ ” Chicago & N.W. Trans. Co. v. Kalo Brick & Tile, 450 US 311, 317, 101 S Ct 1124, 67 L Ed 2d 258 (1981) (quoting Gibbons v. Ogden, 9 Wheat 1, 211, 6 L Ed 23 (1824)). The Court has stated that it is “reluctant to infer pre-emption.” Building & Trades Council v. Associated Builders, 507 US_,_, 113 S Ct 1190, 1194, 122 L Ed 2d 565 (1993). “ ‘Consideration of the Supremacy Clause starts with the basic assumption that Congress did not intend to displace state law.’ ” Ibid, (quoting Maryland v. Louisiana, 451 US 725, 746, 101 S Ct 2114, 68 L Ed 2d 576 (1981)).
Based on those settled preemption principles, we conclude that the case before us does not implicate the Supremacy Clause. The state’s theory is that the federal immigration laws control. We disagree. Nothing that we have found in the immigration laws either expressly, or by implication, touches on the issues in the criminal case that is before us. No decision by this court concerning the lawfulness of defendant’s arrest under Article I, section 9, of the Oregon Constitution possibly could interfere with or otherwise affect the ability of the federal government to administer or enforce its immigration laws. A decision by this court will not impact federal deportation proceedings against defendant, nor will a decision by this court inhibit the INS from employing the administrative warrant procedure in future cases.9 If this court concludes that defendant’s seizure by a federal officer acting pursuant to a valid federal warrant was “unreasonable” under Article I, section 9, the only possible effect of that decision will be on the admissibility of evidence in an Oregon criminal prosecution. Because this court’s interpretation of Article I, section 9, in this context, cannot and will not interfere with the federal government in immigration matters, the Supremacy Clause has no bearing on this case, and this court is not “preempted” from applying Article I, section 9, to defendant’s arrest.
*37 Reasonableness of the Arrest
We turn next to the question whether defendant’s arrest was an “unreasonable” seizure under Article I, section 9. The state has conceded that the arrest warrant did not comply with Article I, section 9, and that the arrest cannot be justified as a reasonable seizure based on the warrant. See supra, 317 Or at 33. The state argues, however, that defendant’s arrest was a reasonable seizure, because it was a permissible warrantless arrest based on probable cause.
In response, defendant does not contend that the INS officer lacked probable cause for his arrest. Defendant contends instead that the arrest was unreasonable under the rule stated by this court in State v. Olson, 287 Or 157, 598 P2d 670 (1979). In Olson, this court held that, under Article I, section 9, “where exigent circumstances which militate against securing [an arrest] warrant do not exist, probable cause to arrest does not justify a forced entry into the home of the suspect.” 287 Or at 165. Defendant argues that the Olson rule applies here, because the use by the INS agent of an invalid arrest warrant to obtain entry to defendant’s apartment was the equivalent of a “forced entry.” Defendant also contends that, “under the facts of this case, there is no federal or state authority allowing a warrantless arrest for violation of federal immigration laws.”10
In this court’s view, however, we need not decide whether defendant’s arrest violated the rule stated in State v. Olson, supra, or whether the arrest was otherwise invalid for lack of statutory authority. Assuming, without deciding, that the arrest was an “unreasonable” seizure under Article I, section 9, we conclude that the guns seized following that arrest were nonetheless admissible in evidence, because defendant consented to the search that uncovered the guns, and that consent was not obtained by exploitation of the unlawful conduct, if any. We turn to a consideration of that point.
*38 Exploitation of Unlawful Police Conduct
We begin our inquiry by making clear that this case does not present the issue whether defendant’s consent to the search of his apartment was voluntary. Rather, this case presents the issue whether defendant’s consent was obtained by exploitation of the purportedly unlawful arrest.11
The distinction that we make here between volun-tariness and exploitation is an important one. Unlawful police conduct12 occurring before a search made pursuant to a person’s consent may affect the admissibility of evidence seized during that search in two ways. In some cases, the unlawful conduct may bear on the issue of voluntariness. That is, the unlawful conduct may have some effect on the state of mind of the person giving the consent, affecting whether the consent is a voluntary act of that person’s free will.13 Where the unlawful conduct bears on the voluntariness of the consent, as in any other case where voluntariness is at issue, the state must prove by a preponderance of the evidence that the consent was voluntary. See, e.g., State v. Paulson, 313 Or 346, 351-52, 833 P2d 1278 (1992) (“Under the consent exception to the warrant requirement, the state *39must prove by a preponderance of the evidence that someone having the authority to do so voluntarily gave the police consent to search the defendant’s person or property.”). If the state fails to meet that burden, then the consent is invalid, and the search is treated as “unreasonable” under Article I, section 9. In that event, evidence seized during the search must be suppressed to vindicate the defendant’s right to be secure against the unreasonable search.
Where, as here, the question of the voluntariness of the consent has not been raised, or where the court has determined that the consent was voluntary, unlawful police conduct occurring before a consent search still may affect the admissibility of evidence seized during that search. This is so because that unlawful conduct — either an unreasonable search or an unreasonable seizure — occurring before the consent search was a violation of the defendant’s rights, even if the consent search by itself was not. Put differently: There may be cases in which suppression of evidence obtained during a consent search may be necessary to vindicate a defendant’s rights that were violated by earlier, unlawful police conduct.
Whether suppression is required in any such case will, however, depend on the nature of the connection between the unlawful police conduct and the evidence sought to be suppressed. As we have noted previously, evidence is subject to suppression in a criminal prosecution if it was “obtained in violation of a defendant’s rights under [Article I, section 9].” State v. Davis, supra, 313 Or at 253 (emphasis supplied). Under that standard, there will have to be, at the very least, a causal connection between the unlawful police conduct and the evidence uncovered during the subsequent consent search. Thus, where the evidence would have been obtained even in the absence of the unlawful police conduct — i.e., where there is no causal connection between the unlawful conduct and the discovery of the evidence — the mere fact that the evidence was obtained after that conduct will not require suppression.
A causal connection alone, however, still is not sufficient to require suppression. This court has rejected the so-called “but for” test, which would require the suppression of any evidence that would not have been discovered “but for” *40the unlawful police conduct. State v. Quinn, 290 Or 383, 394-97, 623 P2d 630 (1981); State v. Kennedy, 290 Or 493, 500-01, 624 P2d 99 (1981). 'Thus, the fact that, “but for” the unlawful conduct, the police would not have been in a position to (for example) seek a person’s consent does not, in and of itself, render any evidence uncovered during the ensuing consent search inadmissible.
In what circumstances, then, does unlawful police conduct render evidence obtained in a later consent search inadmissible, where the consent to the search is voluntary? We think that evidence obtained during such a search should be suppressed only in those cases where the police have exploited their prior unlawful conduct to obtain that consent. Only where such exploitation occurs can it be said that the evidence discovered subsequently was “obtained in violation” of a defendant’s rights under Article I, section 9.
Mere physical presence as a result of prior unlawful conduct does not constitute exploitation of that conduct. Exploitation occurs when the police take advantage of the circumstances of their unlawful conduct to obtain the consent to search. State v. Williamson, 307 Or 621, 772 P2d 404 (1989), provides one example of exploitation. There, during the stop of a pick-up at an unlawful roadblock, the police smelled what they believed to be marijuana in the bed of the pick-up. After the defendant had refused to allow a search, the police told the defendant that, unless he consented to a search, they would detain the vehicle until they could obtain a search warrant. The defendant then consented to the search, and the police discovered marijuana. This court held that the marijuana must be suppressed, because the police “were trading on evidence that they had only by virtue of the unlawful roadblock.” 307 Or at 626.
Although Williamson impliedly was based on a vol-untariness analysis,14 the result in that case may also be *41explained as based on an exploitation analysis. In Williamson, the police were able to obtain the defendant’s consent to the search of his vehicle only by taking advantage of the unlawful roadblock and by telling the defendant that they would detain his vehicle. Thus, the police exploited their unlawful conduct, which was the roadblock. Even if the defendant’s consent were voluntary in light of all the circumstances, the police’s exploitation of their unlawful conduct to obtain that consent would have required suppression of the evidence discovered during the consent search.
The present case, however, is a far cry from Williamson. Here, immediately after the purportedly unlawful arrest, the agent asked defendant if he had any drugs or guns in his apartment.15 Defendant said, “No, go ahead and look.” The agent then confirmed that defendant was giving his consent to a search of the apartment, and defendant said, “Yes, go ahead.” Given those facts, it is apparent that the INS agent did not trade on or otherwise take advantage of the arrest to obtain defendant’s consent to the search. Indeed, there is absolutely nothing in the encounter between the agent and defendant that can be construed as exploitation of the purportedly unlawful arrest. The mere fact that, but for the arrest, the agent would not have been standing in the doorway of defendant’s apartment, in a position to ask defendant about drugs and guns, does not render the evidence discovered in the subsequent consent search inadmissible. See supra, 317 Or at 39-40.
Because, under the facts of this case, the police did not exploit any unlawful conduct to obtain defendant’s consent to the search of his apartment, the guns discovered *42during that search were not “obtained in violation” of defendant’s rights under Article I, section 9, of the Oregon Constitution. Therefore, the guns were not subject to suppression on the grounds argued by defendant. The Court of Appeals erred in concluding otherwise.
FEDERAL CONSTITUTIONAL ANALYSIS
Defendant argues that the administrative arrest warrant used to secure his arrest violated the Fourth Amendment to the Constitution of the United States, because it was not “supported by oath or affirmation.” Defendant contends that, therefore, his arrest was invalid and that the guns must be suppressed as the “fruit” of the invalid arrest. For the reasons that follow, we disagree.
The Fourth Amendment provides:
“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”
Although the Supreme Court of the United States never has ruled on the validity of the administrative arrest warrants used to detain deportable aliens, the Court has suggested its approval of those warrants on at least one occasion. In Abel v. United States, 362 US 217, 80 S Ct 683, 4 L Ed 2d 668 (1960), the defendant moved to suppress evidence obtained during a warrantless search made in connection with the defendant’s arrest pursuant to an administrative warrant of the type at issue here. The Court declined to decide whether such warrants satisfy the oath or affirmation requirement of the Fourth Amendment, because the defendant had not raised the issue below. In explaining its decision not to rule on the question, however, the Court stated:
“Statutes authorizing administrative arrest to achieve deportation proceedings have the sanction of time. It would emphasize the disregard for the presumptive respect the Court owes to the validity of Acts of Congress, especially when confirmed by uncontested historical legitimacy, to bring into question for the first time such a long-sanctioned practice of government at the behest of a party who not only *43did not challenge the exercise of authority below, but expressly acknowledged its validity.
“Statutes providing for deportation have ordinarily authorized the arrest of deportable aliens by order of an executive official. The first of these was in 1798. * * * To be sure, some of these statutes * * * dealt only with aliens who had landed illegally in the United States, and not with aliens sought to be deported by reason of some act or failure to act since entering. Even apart from these, there remains overwhelming historical legislative recognition of the propriety of administrative arrest for deportable aliens such as petitioner.”
362 US at 230, 233.
The Supreme Court has not had occasion to revisit the question that it declined to answer in Abel. However, at least one federal court has held, in reliance on Abel, that INS administrative warrants do not violate the oath or affirmation requirement of the Fourth Amendment. See Spinella v. Esperdy, 188 F Supp 535 (SD NY 1960) (so holding). Moreover, the Supreme Court has made clear that ‘ ‘ [a] deportation proceeding is a purely civil action” and that, as a result, “various protections that apply in the context of a criminal trial do not apply in a deportation hearing.” INS v. Lopez-Mendoza, 468 US 1032, 1038, 104 S Ct 3479, 82 L Ed 2d 778 (1984).
In the light of Abel and the unquestioned recognition by the Supreme Court that aliens subject to deportation proceedings do not enjoy the full panoply of constitutional protections accorded to persons subject to criminal prosecution, we conclude that the administrative arrest warrant issued to procure defendant’s arrest as a deportable alien in this case did not violate the Fourth Amendment. Consequently, defendant’s arrest was not “unreasonable” under that constitutional provision.
Only one possible question remains under the federal constitution. Defendant has argued that his consent to the search of his apartment was subject to suppression as the “fruit” of his purportedly unlawful arrest. We have concluded that defendant’s arrest was not unlawful under the Fourth Amendment; however, we have assumed, for the sake *44of our analysis of state constitutional law, that defendant’s arrest was unlawful under Article I, section 9, of the Oregon Constitution. Given that assumption, the question remaining is this: In determining whether an item of evidence is subject to suppression under the Fourth Amendment as the “fruit” of a prior illegality,16 is an arrest that violates a state constitutional provision but not the Fourth Amendment itself treated as a “prior illegality” for purposes of that analysis? For the following reason, we conclude that the answer to that question is “no.”
In California v. Greenwood, 486 US 35, 108 S Ct 1625, 100 L Ed 2d 30 (1988), the Supreme Court held that the Fourth Amendment does not grant a right to be secure against the warrantless search and seizure of garbage left outside the curtilage of a home. The defendant in that case pointed out to the Court that the California Constitution does grant such a right; however, the California Constitution does not permit the suppression of evidence as a means of enforcing that right. The defendant, therefore, argued that the Fourth Amendment itself should vindicate the defendant’s state constitutional right. The Court rejected that argument, writing as follows:
“Individual States may surely construe their own constitutions as imposing more stringent constraints on police conduct than does the Federal Constitution. We have never intimated, however, that whether or not a search is reasonable within the meaning of the Fourth Amendment depends on the law of the particular State in which the search occurs. * * * Respondent’s argument is no less than a suggestion that concepts of privacy under the laws of each State are to determine the reach of the Fourth Amendment. We do not accept this submission.”
486 US at 43-44.
Greenwood stands for the proposition that the Fourth Amendment does not exist to vindicate violations of state constitutional law. Evidence is not subject to suppression under the Fourth Amendment unless a violation of that provision has occurred. Because the arrest in this case did not *45violate the Fourth Amendment, the guns discovered in the subsequent consent search were not subject to suppression under the Fourth Amendment, even if the arrest violated Article I, section 9, of the Oregon Constitution (a question that we have not resolved in this case).
CONCLUSION
The guns seized during the search of defendant’s apartment were not subject to suppression under statutory-law, the Oregon Constitution, or the Constitution of the United States. The Court of Appeals erred in concluding to the contrary.
The decision of the Court of Appeals is reversed. The judgment of the circuit court is affirmed.
Pending a determination of deportability, an alien “may, upon warrant of the Attorney General, be arrested and taken into custody.” 8 USC § 1252(a)(1) (1988).
Federal regulations permit various INS officials, including an Assistant District Director for Investigations, to issue arrest warrants for aliens. 8 CFR § 242.2(c)(iv).
In 1989, the legislature amended ORS 166.270 to change the name of the crime to “felon in possession of a firearm.” Or Laws 1989, ch 839, § 4.
On appeal and review, defendant maintains that the guns should have been suppressed, hut he does not mention the statements.
Article I, section 9, of the Oregon Constitution provides, in part, that “no warrant shall issue but upon probable cause, supported by oath, or affirmation. ’’The Fourth Amendment to the Constitution of the United States provides, in part, that “no Warrants shall issue, but upon probable cause, supported by Oath or affirmation.” The Fourth Amendment applies to the states through the Due Process Clause of the Fourteenth Amendment. Mapp v. Ohio, 367 US 643, 81 S Ct 1684, 6 L Ed 2d 1081 (1961).
A dissenting judge would have affirmed on the basis that the trial court properly denied the motion to suppress, because defendant’s consent was voluntary, in spite of the unlawful arrest. See State v. Rodriguez, 110 Or App 544, 551-53, 823 P2d 1026 (1992) (Rossman, J., dissenting).
Initially, the state argued that the certified copy of defendant’s record of conviction, which was shown to the INS official who issued the warrant, was sufficient to satisfy the oath or affirmation requirement of Article I, section 9. The state later acknowledged, however, that the record of conviction did not contain any information from which the official who issued the warrant could have determined that defendant was an alien — a fact necessary to establish probable cause for defendant’s arrest as a deportable alien. Because of the state’s concession, we need not decide here whether a court-certified copy of a conviction record is a sufficient “oath or affirmation” under Article I, section 9, for purposes of establishing the fact of a conviction.
Defendant has never contended that the arrest warrant was deficient under the applicable federal statutes and regulations. Defendant does contend, however, that the warrant violated the oath or affirmation requirement of the Fourth Amendment to the Constitution of the United States. We discuss that issue infra, 317 Or at 42-43. At this point, however, for purposes of addressing the state’s Supremacy Clause argument, we simply assume the validity of the warrant under federal law.
If, citing Article I, section 9, of the Oregon Constitution, an alien were to seek an injunction against a pending arrest pursuant to an INS warrant, then a preemption issue might well be presented due to the potential interference with the federal government’s purposes and objectives. Cf. In re Neagle, 135 US 1, 10 S Ct 658, 34 L Bd 55 (1890) (state criminal prosecution against federal marshal for acts committed by marshal in line of duty). However, this is not such a case.
Under federal statutory law, an INS agent may arrest an alien without a warrant “if he has reason to believe that the alien so arrested is in the United States in violation of any [immigration] law or regulation and is likely to escape before a warrant can be obtained for his arrest.” 8 USC § 1357(a)(2) (1988). Defendant contends that the INS agent in this case “lacked any reason to believe defendant was likely to escape before he could procure a warrant, because he did obtain one.”
In the trial court, when the state raised the issue of defendant’s consent to the search, defendant did not argue that his consent was involuntary. Instead, defendant argued only that the evidence seized in the search was the “fruit” of the unlawful arrest. On appeal, defendant has attempted to argue both that his consent was involuntary and that the evidence was the “fruit” of the unlawful arrest. We decline to address the voluntariness of defendant’s consent, because that issue was not preserved for this court’s review. See Ailes v. Portland Meadows, Inc., 312 Or 376, 380, 823 P2d 956 (1991) (“Generally, before an appellate court may address whether a trial court committed an error in any of the particulars of the trial of a case, the adversely affected party must have preserved the alleged error in the trial court.”).
By “unlawful police conduct,” we mean an act by a government entity or its agent that violates a defendant’s rights under Article I, section 9, of the Oregon Constitution.
Generally, this result will occur where the circumstances of the unlawful conduct are coercive in nature, without regard to the unlawfulness itself. For instance, suppose that a dozen police officers burst into a person’s home in the dead of night, rouse that person from bed and, with guns drawn, seek that person’s consent to search the basement of the house. If the person consents, that consent may well be involuntary — i.e., not an act of that person’s free will — regardless of whether the police had legal authority to do what they did. A second, less likely scenario would be one in which the officers’ acts are not threatening, but the person whose consent is sought knows that the officers’ acts nonetheless are illegal. The effect (if any) of knowledge of the illegality on the voluntariness ofaconsent would be a factual issue for resolution by the trial judge.
The court never stated expressly that the statement by the police that they would detain the defendant’s vehicle rendered the defendant’s consent “involuntary.” However, the tenor of the opinion suggests that it was based on grounds of voluntariness, rather than simply exploitation. For example, the court stated:
“This case again pits the ‘voluntariness’ of a defendant’s incriminating disclosure against the judicial assessment of acts leading to that disclosure, and it again shows that while the events and their psychic effects may be questions of *41fact, the legal effect of the ‘voluntary’ disclosure remains a legal, not a factual, judgment.”
State v. Williamson, 307 Or 621, 625, 772 P2d 404 (1989).
The majority in the Court of Appeals concluded that this question was “unwarranted,” because defendant was “cooperative” and the agent “expressed no articulable concern for his safety.” State v. Rodriquez, supra, 110 Or App at 551. That may be true; however, the question itself was not unlawful. Defendant had been read his Miranda rights and stated that he understood them. He was under no compulsion to answer the agent’s question.
For a discussion of the “fruit of the poisonous tree” doctrine under the Fourth Amendment to the Constitution of the United States, see Wong Sun v. United States, 371 US 471, 83 S Ct 407, 9 L Ed 2d 441 (1963).