This case arises from a John Doe investigation into fund-raising activities in Rock county. Judge Edwin C. Dahlberg, the presiding judge at the John Doe proceeding, issued a material witness arrest warrant for James Beryl Brady. Brady was arrested pursuant to the warrant and consented to a search of his premises. After being warned of his Miranda rights, he voluntarily made allegedly inculpa-tory statements. The state then charged Brady with theft by fraud, contrary to sec. 943.20(l)(d), Stats., based upon the evidence discovered immediately after the arrest.
Brady moved the circuit court for Rock county, Judge J. Richard Long, to suppress the evidence discovered after the arrest. He asserted that his arrest was illegal because the John Doe judge lacked authority to issue a material witness arrest warrant. The circuit court agreed that a John Doe judge lacks authority to issue material witness arrest warrants under sec. 969.01(3), Stats. Although Brady consented to the search and voluntarily made his statement, the circuit court ruled that the evidence had to be suppressed because it was the fruit of an illegal arrest, an arrest pursuant to an invalid material witness arrest warrant. See Taylor v. Alabama, 457 U.S. 687 (1982). The court of appeals affirmed the circuit court order. State v. Brady, 118 Wis. 2d 154, 345 N.W.2d 533 (Ct. App. 1984). We denied the state's petition for review.
*446After our denial of the state's petition for review, the Supreme Court handed down its decision in United States v. Leon, 468 U.S. 897, 104 S. Ct. 3405 (1984). In Leon the Supreme Court adopted a good-faith exception to the exclusionary rule. Based on the Supreme Court's recognition of a good-faith exception to the exclusionary rule, the state asked the circuit court to reconsider its suppression order, arguing that Brady was arrested in good-faith reliance on the material witness arrest warrant. The circuit court refused to consider whether the good-faith exception should apply to Brady's arrest, however, because it concluded that the court of appeals' affirmance of the suppression order established the suppression order as the law of the case. The state appealed the circuit court's order denying its motion for reconsideration. We accepted this case on certification from the court of appeals, pursuant to sec. (Rule) 809.61, Stats.
A material witness arrest warrant cannot be issued in violation of the fourth amendment's prohibition against unreasonable searches and seizures. See Bacon v. United States, 449 F.2d 933, 942-43 (9th Cir. 1971). A material witness arrest warrant is invalid if it is not based on probable cause. Before we reach the issue of whether the material witness arrest warrant was valid, however, we must decide whether the law of the case doctrine precludes the circuit court from reconsidering the suppression order that the court of appeals affirmed.
The state acknowledges that the law of the case doctrine generally restrains a circuit court from reconsidering an order that an appellate court has affirmed. *447"[A] decision on an issue of law made at one stage of a case becomes a binding precedent to be followed in successive stages of the same litigation." 1B Moore's Federal Practice par. 0.404[1] at 117 (2d ed. 1984).
The state makes two arguments to support its assertion that the law of the case doctrine should not preclude reconsideration in these circumstances. First, the state argues that the issue upon which it seeks reconsideration, adoption of a good-faith exception, was not decided in the prior appeal. Second, it contends that the change in the law manifested in Leon comes within an exception to the general rule restricting reconsideration.
Brady maintains that the suppression order is the law of the case because of the court of appeals' affir-mance. He argues that the circuit court is prohibited from modifying or reviewing the suppression order in any respect. Granting that a circuit court may have the power to reconsider a prior order in some circumstances, Brady argues that the court is not obliged to do so and did not abuse its discretion in refusing to reconsider its suppression order in this case.
In McGovern v. Eckhart, 200 Wis. 64, 227 N.W. 300 (1929), we departed from our tradition of rigid adherence to the law of the case doctrine and held that we could reconsider a prior ruling in a case "whenever cogent, substantial, and proper reasons exist." Id. at 78. "[I]t is within the power of the courts to disregard the rule of 'law of the case' in the interests of justice." Id. at 75. The McGovern case, however, did not speak expressly to the issue of a circuit court's authority to reconsider a decision that an appellate court had affirmed at an earlier stage in the proceedings. Nonetheless, two of the reasons for allowing an appel*448late court to reconsider its earlier decision in a case apply with equal force to allow a circuit court to reconsider its decision even after an appellate court has affirmed the decision:
"[A] decision of a legal issue or issues by an appellate court establishes the 'law of the case1 and must be followed in all subsequent proceedings in the same case in the trial court or on a later appeal in the appellate court, unless the evidence on a subsequent trial was substantially different, [or] controlling authority has since made a contrary decision of the law applicable to such issues." White v. Murtha, 377 F.2d 428, 431-32 (5th Cir. 1967).
To conclude that a circuit court has the authority, in some circumstances, to reconsider an order affirmed by an appellate court does not compel the conclusion that the circuit court must reconsider such an order whenever those circumstances arise. Because the law of the case is a question of court practice, and not an inexorable rule, McGovern, 200 Wis. 2d at 75-76, it requires the exercise of judicial discretion. While the circuit court may have acted within its discretion in denying the state's motion for reconsideration in this case, however, it is within our discretion, now that the case is before us, to review any issues of law which the case presents. We declined to review the issues on the merits during the initial appeal of the nonfinal suppression order. Subsequently, the Supreme Court issued its decision in Leon in which it created a good-faith exception to the exclusionary rule. The court of appeals certified this case to us in light of the Leon decision. Accordingly, we choose to exercise our authority to review the propriety of the circuit court's suppression order.
*449Having concluded that the law of the case doctrine does not preclude reconsideration of the suppression order, we turn our attention to the validity of the material witness arrest warrant. Judge Dahlberg issued the material witness arrest warrant under sec. 969.01(3), Stats., which authorizes the issuance of such warrants only in felony criminal proceedings. Section 969.01(3) states as follows: "If it appears by affidavit that the testimony of a person is material in any felony criminal proceeding and that it may become impracticable to secure his presence by subpoena, the judge may require such person to give bail for his appearance as a witness." (Emphasis added.)
The circuit court concluded that the arrest warrant was invalid and ordered the suppression of any evidence which resulted from the arrest because the court believed that a John Doe proceeding does not fit within the definition of a felony criminal proceeding. The court equated a "criminal proceeding" to a "criminal action." Relying upon sec. 968.02(2), Stats., which provides that a criminal action commences with the filing of a criminal complaint, the court concluded that a John Doe proceeding is not a "criminal proceeding" because it is not commenced by a formal complaint. The court of appeals affirmed, holding that a John Doe proceeding is not a "felony" criminal proceeding because the classification of any alleged criminal conduct is not resolved until a complaint is filed.
The state maintains that the material witness arrest warrant was valid. The state argues that Judge Dahlberg had authority to issue a warrant under sec. 969.01(3), Stats., because this John Doe proceeding was a felony criminal proceeding. Even if sec. 969.01(3) were construed not to enable a judge in a John Doe pro*450ceeding to issue such warrants, the state asserts that a John Doe judge has inherent authority to issue material witness arrest warrants.
Brady argues that the material witness arrest warrant was invalid. He contends that a John Doe judge does not have authority to issue such warrants under sec. 969.01(3), Stats., because a John Doe proceeding is not a felony criminal proceeding. Moreover, Brady asserts that, whether the judge issued the material witness arrest warrant under the statute or by virtue of his inherent authority, the warrant must be deemed invalid because the state did not show that it was unable to obtain Brady's presence by subpoena.
Were we to accept the state's argument and hold that a John Doe judge has either the statutory authority or the inherent authority to issue material witness arrest warrants, our resolution of that question would not be dispositive. Regardless of which authority Judge Dahlberg relied upon in issuing Brady's material witness arrest warrant, this case turns on a more fundamental question — whether the warrant was issued in conformity with the fourth amendment's requirement of probable cause.
A material witness arrest warrant cannot be issued in violation of the fourth amendment's prohibition against unreasonable searches and seizures. See Bacon v. United States, 449 F.2d at 942-43. The fourth amendment requires probable cause for an arrest. "Before a material witness arrest warrant may issue, the judicial officer must have probable cause to believe (1) 'that the testimony of a person is material' and (2) 'that it may become impracticable to secure his presence by subpoena.'" Id. at 943. See Barry v. United States ex rel. *451Cunningham, 279 U.S. 597, 617-18 (1929) [quoting Crosby v. Potts, 8 Ga. App. 463, 468, 69 S.E. 582 (1910)]. See also sec. 969.01(3), Stats.
Judge Dahlberg issued the material witness arrest warrant in reliance upon an affidavit prepared by Captain Pittner of the City of Beloit Police Department.1 *452While the affidavit does offer a basis upon which Judge Dahlberg could have found probable cause that Brady's testimony would be material to the John Doe proceeding, it does not offer a basis upon which Judge Dahl-berg could have found probable cause that it would be impracticable to secure Brady's presence by subpoena.
The affidavit contains nothing resembling an affirmative assertion that the police had tried to obtain Brady's presence by subpoena or that the police had reason to believe that obtaining his presence by subpoena would be impracticable. The affidavit indicates that Brady is from West Virginia and had been in Be-loit for only eight days, but that in itself is not a sufficient basis for the judge to find that Brady was likely to leave the state or unlikely to respond to a subpoena, especially when the affidavit also indicates that Brady was entirely cooperative when Captain Pittner talked with him two days prior to the issuance of the material witness arrest warrant. Notably, the material witness arrest warrant itself states that Judge Dahlberg found probable cause only with regard to Brady's status as a material witness.
*453Because the affidavit did not offer a basis to find probable cause that securing Brady's presence through a subpoena would be impracticable, the material witness arrest warrant which Judge Dahlberg issued in reliance upon the affidavit was invalid. Because the arrest warrant was invalid, Brady's arrest violated the fourth amendment prohibition against unreasonable searches and seizures. The circuit court acted properly in suppressing the evidence obtained as a result of the illegal arrest.
Relying upon the Supreme Court's decision in United States v. Leon, supra, however, the state argues that even if the arrest was illegal, suppression of the evidence is an inappropriate remedy because the officers acted in good-faith reliance upon the material witness arrest warrant in arresting Brady. Leon created a good-faith exception to the exclusionary rule. The exception applies in situations in which the exclusion of evidence would not promote the exclusionary rule's purpose, which is to deter police conduct in violation of the fourth amendment. 104 S. Ct. at 3412-22. The state urges us to adopt Leon and to overrule our holding in Hoyer v. State, 180 Wis. 407, 193 N.W. 89 (1923), in which we adopted an exclusionary rule based upon the Wisconsin Constitution. Brady contends that this case is inappropriate for consideration of a good-faith exception to the exclusionary rule because the record does not support a finding that the police acted in good faith. Relying upon our decision in Conrad v. State, 63 Wis. 2d 616, 218 N.W.2d 252 (1974), however, Brady further argues that because the legislature has sanctioned the exclusionary rule, see sec. 971.31, Stats., *454only the legislature can repeal or change the exclusionary rule. Conrad, 63 Wis. 2d at 637.
We conclude that this case is not a proper vehicle for deciding whether to adopt a good-faith exception to the exclusionary rule. In Leon the Supreme Court expressly acknowledged that an officer would not "manifest objective good faith in relying on a warrant based on an affidavit 'so lacking in indicia of probable cause as to render official belief in its existence entirely unreasonable.' " Leon, 104 S. Ct. at 3422 [quoting Brown v. Illinois, 422 U.S. 590, 611 (1975) (Powell, J., concurring in part)]. The fourth amendment requires that the affidavit upon which the warrant was based had to contain sufficient facts to support a finding of probable cause regarding the impracticability of securing Brady's presence through a subpoena. Because the affidavit lacked indicia of probable cause regarding the impracticability of securing Brady's presence through a subpoena, this case does not present a question of "good faith." Therefore, Leon is not implicated. Accordingly, we do not decide whether to adopt a good-faith exception to the exclusionary rule in Wisconsin. We hold that the circuit court acted properly in suppressing the evidence discovered as a result of the illegal arrest of Brady.
By the Court. — The order of the circuit court is affirmed.
The affidavit of Captain Pittner states as follows:
"I, Truett Pittner, being first duly sworn, on oath deposes and states as follows:
"1. That I am Captain of detectives for the City of Beloit Police Department and have been a police officer for the City of Beloit Police Department for approximately fifteen (15) years and that I have total police experience of approximately eighteen (18) years; that your affiant has been conducting an investigation into a solicitation scheme that is being conducted in Beloit, Rock County, Wisconsin, and that in connection with that scheme, he talked with a subject who identified himself as James Brady and Brady informed him that he was the promoter of this scheme and that he was from Morgantown, West Virginia and that he has been in the City of Beloit for only eight (8) days and that he had retained Linda Hurley, amongst others, to operate telephone banks to solicit funds within the greater Beloit community and that this was done under the guise of being a charitable contribution for the Kiwanis Club of Greater Beloit and that he expected to net $27,465.00 and of that amount approximately $4,000.00 would go to the Kiwanis Club and that the remainder would go to Linda Hurley and her telephone solicitors, himself and to the show that is to be put on and attended by handicapped children; Brady further stated that Linda Hurley gets 15% of the solicitations she takes in and that he gets 35% for his promoter[']s fees and the remainder is split as previously mentioned; that your affiant talked to Brady on May 19, 1982; and Brady further stated that he does not go out and actively solicit various organizations to give handicapped children tickets to the show that is being arranged but if any organization contacts him that does represent handicapped children, he would give them tickets;
"2. That your affiant has a copy of the sales pitch used in this *452game and the sales pitch stresses that the money donated is for tickets for handicapped children;
"3. That your affiant spoke with a citizen informant who identified herself to him and this citizen informant told him that she was contacted by a solicitor in this game and that the solicitor informed her, amongst other things, that this solicitation originally started as a solicitation for the Kiwanis Club of Greater Beloit and that she ask[ed] the solicitor if this was in any way affiliated with the Beloit Police Department and received a yes answer to that;
"4. That your affiant has seen the automobile driven by the aforementioned Brady and that this automobile bears license plates from West Virginia."