delivered the opinion of the Court.
Congress has provided that “[a]ny officer of the customs may at any time go on board of any vessel... at any place in the United States . . . and examine the manifest and other documents and papers . . . and to this end may hail and stop such vessel . . . and use all necessary force to compel compliance.” 46 Stat. 747, as amended, 19 U. S. C. § 1581(a).1 We are asked to decide whether the Fourth Amendment is offended when customs officials, acting pursuant to this *581statute and without any suspicion of wrongdoing, board for inspection of documents a vessel that is located in waters providing ready access to the open sea.2
*582Near midday on March 6, 1980, customs officers, accompanied by Louisiana state policemen, were patrolling the Calca-sieu River Ship Channel, some 18 miles inland from the gulf coast, when they sighted the Henry Morgan II, a 40-foot sailboat, anchored facing east on the west side of the channel. The Calcasieu River Ship Channel is a north-south waterway connecting the Gulf of Mexico with Lake Charles, Louisiana. Lake Charles, located in the southwestern corner of Louisiana, is a designated Customs Port of Entry in the Houston, Texas Region. While there is access to the channel from Louisiana’s Calcasieu Lake, the channel is a separate thoroughfare to the west of the lake which all vessels moving between Lake Charles and the open sea of the Gulf must traverse.
Shortly after sighting the sailboat, the officers also observed a large freighter moving north in the channel. The freighter was creating a huge wake and as it passed the Henry Morgan II the wake caused the smaller vessel to rock violently from side to side. The patrol boat then approached the sailboat from the port side and passed behind its stern. *583On the stern the name of the vessel, the “Henry Morgan II,” was displayed along with its home port, “Basilea.” The officers sighted one man, respondent Hamparian, on deck. Officer Wilkins twice asked if the sailboat and crew were all right. Hamparian shrugged his shoulders in an unresponsive manner.
Officer Wilkins, accompanied by Officer Dougherty of the Louisiana State Police, then boarded the Henry Morgan II and asked to see the vessel’s documentation. Hamparian handed Officer Wilkins what appeared to be a request to change the registration of a ship from Swiss registry to French registry, written in French and dated February 6, 1980. It subsequently was discovered that the home port designation of “Basilea” was Latin for Basel, Switzerland; the vessel was, however, of French registry.
While examining the document, Officer Wilkins smelled what he thought to be burning marihuana. Looking through an open hatch, Wilkins observed burlap-wrapped bales that proved to be marihuana. Respondent Villamonte-Marquez was on a sleeping bag atop of the bales. Wilkins arrested both Hamparian and Villamonte-Marquez and gave them Miranda warnings. A subsequent search revealed some 5,800 pounds of marihuana on the Henry Morgan II, stored in almost every conceivable place including the forward, mid, and aft cabins, and under the seats in the open part of the vessel.
A jury found respondents guilty of conspiring to import marihuana in violation of 21 U. S. C. § 963, importing marihuana in violation of 21 U. S. C. § 952(a), conspiring to possess marihuana with intent to distribute in violation of 21 U. S. C. § 846, and possessing marihuana with intent to distribute in violation of 21 U. S. C. § 841(a)(1). The Court of Appeals for the Fifth Circuit reversed the judgment of conviction, finding that the officers’ boarding of the Henry Morgan II “was not reasonable under the fourth amendment” because the boarding occurred in the absence of “a reasonable *584suspicion of a law violation.” 652 F. 2d 481, 488 (1981). Because of a conflict among the Circuits and the importance of the question presented as it affects the enforcement of customs laws, we granted certiorari. 457 U. S. 1104 (1982).3 We now reverse.
In 1790 the First Congress enacted a comprehensive statute “to provide more effectually for the collection of the duties imposed by law on goods, wares and merchandise imported into the United States, and on the tonnage of ships or vessels.” Act of Aug. 4, 1790, 1 Stat. 145. Section 31 of that Act provided in pertinent part as follows:
“That it shall be lawful for all collectors, naval officers, surveyors, inspectors, and the officers of the revenue cutters herein after mentioned, to go on board of ships or vessels in any part of the United States, or within four leagues of the coast thereof, if bound to the United States, whether in or out of their respective districts, for the purposes of demanding the manifests aforesaid, and of examining and searching the said ships or vessels . . . .” 1 Stat. 164.
This statute appears to be the lineal ancestor of the provision of present law upon which the Government relies to sustain *585the boarding of the vessel in this case. Title 19 U. S. C. § 1581(a) provides that “[a]ny officer of the customs may at any time go on board of any vessel ... at any place in the United States or within the customs waters . . . and examine the manifest and other documents and papers . . . .”
The Government insists that the language of the statute clearly authorized the boarding of the vessel in this case. The respondents do not seriously dispute this contention, but contend that even though authorized by statute the boarding here violated the prohibition against unreasonable searches and seizures contained in the Fourth Amendment to the United States Constitution. We of course agree with respondents’ argument that “no Act of Congress can authorize a violation of the Constitution.” Almeida-Sanchez v. United States, 413 U. S. 266, 272 (1973). But we also agree with the Government’s contention that the enactment of this statute by the same Congress that promulgated the constitutional Amendments that ultimately became the Bill of Rights gives the statute an impressive historical pedigree.4 United *586States v. Ramsey, 431 U. S. 606 (1977). As long ago as the decision in Boyd v. United States, 116 U. S. 616 (1886), this Court said:
“The seizure of stolen goods is authorized by the common law . . . and the like seizures have been authorized by our own revenue acts from the commencement of the government. The first statute passed by Congress to regulate the collection of duties, the act of July 31, 1789, 1 Stat. 29, 43, contains provisions to this effect. As this *587Act was passed by the same Congress which proposed for adoption the original amendments to the Constitution, it is clear that the members of that body did not regard searches and seizures of this kind as ‘unreasonable,’ and they are not embraced within the prohibition of the amendment.” Id., at 623 (emphasis supplied; footnote omitted).
In holding that the boarding of the vessel without articula-ble suspicion violated the Fourth Amendment, the Court of Appeals relied on several of its own decisions and on our decision in United States v. Brignoni-Ponce, 422 U. S. 873 (1975), where we said:
“Except at the border and its functional equivalents, officers on roving patrol may stop vehicles only if they are aware of specific articulable facts, together with rational inferences from those facts, that reasonably warrant suspicion that the vehicles contain aliens who may be illegally in the country.” Id., at 884.
We think that two later decisions also bear on the question before us.
In United States v. Martinez-Fuerte, 428 U. S. 543 (1976), we upheld the authority of the Border Patrol to maintain permanent checkpoints at or near intersections of important roads leading away from the border at which a vehicle would be stopped for brief questioning of its occupants “even though there is no reason to believe the particular vehicle contains illegal aliens.” Id., at 545. Distinguishing our holding in United States v. Brignoni-Ponce, supra, we said:
“A requirement that stops on major routes inland always be based on reasonable suspicion would be impractical because the flow of traffic tends to be too heavy to allow the particularized study of a given car that would enable it to be identified as a possible carrier of illegal aliens. In particular, such a requirement would largely eliminate any deterrent to the conduct of *588well-disguised smuggling operations, even though smugglers are known to use these highways regularly.” 428 U. S., at 557.
Three Terms later we held in Delaware v. Prouse, 440 U. S. 648 (1979), that “persons in automobiles on public roadways may not for that reason alone have their travel and privacy interfered with at the unbridled discretion of police officers.” Id., at 663. We added that alternative methods, such as spot checks that involve less intrusion, or questioning of all oncoming traffic at roadblock-type stops, would just as readily accomplish the State’s objectives in furthering compliance with auto registration and safety laws.
Our focus in this area of Fourth Amendment law has been on the question of the “reasonableness” of the type of governmental intrusion involved. “Thus, the permissibility of a particular law enforcement practice is judged by balancing its intrusion on the individual’s Fourth Amendment interests against its promotion of legitimate governmental interests.” Delaware v. Prouse, supra, at 654. See also Camara v. Municipal Court, 387 U. S. 523 (1967); Terry v. Ohio, 392 U. S. 1 (1968); Cady v. Dombrowski, 413 U. S. 433 (1973); United States v. Brignoni-Ponce, supra; United States v. Martinez-Fuerte, supra. It seems clear that if the customs officers in this case had stopped an automobile on a public highway near the border, rather than a vessel in a ship channel, the stop would have run afoul of the Fourth Amendment because of the absence of articulable suspicion. See United States v. Brignoni-Ponce, supra. But under the overarching principle of “reasonableness” embodied in the Fourth Amendment, we think that the important factual differences between vessels located in waters offering ready access to the open sea and automobiles on principal thoroughfares in the border area are sufficient to require a different result here.
The difference in outcome between the roving patrol stop in Brignoni-Ponce, supra, and the fixed checkpoint stop in *589Martinez-Fuerte, supra, was due in part to what the Court deemed the less intrusive and less awesome nature of fixed checkpoint stops when compared to roving patrol stops. And the preference for roadblocks as opposed to random spot checks expressed in Delaware v. Prouse, supra, reflects a like concern. But no reasonable claim can be made that permanent checkpoints would be practical on waters such as these where vessels can move in any direction at any time and need not follow established “avenues” as automobiles must do. Customs officials do not have as a practical alternative the option of spotting all vessels which might have come from the open sea and herding them into one or more canals or straits in order to make fixed checkpoint stops. Smuggling and illegal importation of aliens by land may, and undoubtedly usually does, take place away from fixed checkpoints or ports of entry, but much of it is at least along a finite number of identifiable roads. But while eventually maritime commerce on the inland waters of the United States may funnel into rivers, canals, and the like, which are more analogous to roads and make a “roadblock” approach more feasible, such is not the case in waters providing ready access to the seaward border, beyond which is only the open sea.
Respondents have asserted that permanent checkpoints could be established at various ports. But vessels having ready access to the open sea need never come to harbor. Should the captain want to avoid the authorities at port, he could carry on his activity by anchoring at some obscure location on the shoreline, or, as may have been planned in this case, the captain could transfer his cargo from one vessel to another. In cases involving such endeavors as fishing or water exploration, the crew of the vessel can complete its mission without any assistance.
Quite apart from the aforementioned differences between waterborne vessels and automobiles traveling on highways, the documentation requirements with respect to vessels are significantly different from the system of vehicle licensing *590that prevails generally throughout the United States. A police officer patrolling a highway can often tell merely by observing a vehicle’s license plate and other outward markings whether the vehicle is currently in compliance with the requirements of state law. See Delaware v. Prouse, supra, at 660-661. No comparable “license plates” or “stickers” are issued by the United States or by States to vessels. Both of the required exterior markings on documented vessels — the name and hailing port — as well as the numerals displayed by undocumented American boats, are marked on the vessel at the instance of the owner. Furthermore, in cases like this one where the vessel is of foreign registry it carries only the markings required by its home port. Here those markings indicated that the vessel was of Swiss registry, while in actuality it carried French documentation papers.
The panoply of statutes and regulations governing maritime documentation are likewise more extensive and more complex than the typical state requirements for vehicle licensing; only some of the papers required need explicit mention here to illustrate the point. All American vessels of at least five tons and used for commercial purposes must have a “certificate of documentation.” In addition, vessels engaged in certain trades must obtain special licenses. While pleasure vessels of this size are not required to be documented, they are eligible for federal registration. See 46 U. S. C. § 65 et seq. (1976 ed., Supp. V). Many of these vessels must also submit to periodic inspection by the Coast Guard and a “certificate of inspection” must be kept on the vessel at all times. 46 U. S. C. §§399, 400. Smaller American vessels cannot be issued federal documentation papers, but under federal law each such vessel with propulsion machinery must have a state-issued number displayed on a “certificate of number” that must be available for inspection at all times. 46 U. S. C. § 1470. Vessels not required to carry federal documentation papers also may be required to carry a state-issued safety certificate. 46 U. S. C. § 1471.
*591While foreign vessels are not required to carry federal documentation papers, they are required to have a “manifest,” which must be delivered to customs officials immediately upon arrival in this country. 19 U. S. C. § 1439. If a foreign vessel wants to visit more than one customs district, it must obtain a “permit to proceed” at its first port of call, with the exception that a foreign yacht need not obtain such a permit if it has been issued a “cruising license.” 46 U. S. C. § 313; 19 U. S. C. § 1435. Any vessel departing American waters for a foreign port must deliver its “manifest” to Customs and obtain clearance. 46 U. S. C. § 91.
These documentation laws serve the public interest in many obvious ways and respondents do not suggest that the public interest is less than substantially furthered by enforcement of these laws. They are the linchpin for regulation of participation in certain trades, such as fishing, salvaging, towing, and dredging, as well as areas in which trade is sanctioned, and for enforcement of various environmental laws. The documentation laws play a vital role in the collection of customs duties and tonnage duties. They allow for regulation of imports and exports assisting, for example, Government officials in the prevention of entry into this country of controlled substances, illegal aliens, prohibited medicines, adulterated foods, dangerous chemicals, prohibited agricultural products, diseased or prohibited animals, and illegal weapons and explosives. These interests are, of course, most substantial in areas such as the ship channel in this case, which connects the open sea with a Customs Port of Entry. Cf. United States v. Ramsey, 431 U. S. 606 (1977). Requests to check certificates of inspection play an obvious role in ensuring safety on American waterways. While inspection of a vessel’s documents might not always conclusively establish compliance with United States shipping laws, more often than not it will.5
*592While the need to make document checks is great,6 the resultant intrusion on Fourth Amendment interests is quite limited. While it does intrude on one’s ability to make “ ‘free passage without interruption,”’ United States v. Martinez-Fuerte, 428 U. S., at 557-558 (quoting Carroll v. United States, 267 U. S. 132, 154 (1925)), it involves only a brief detention where officials come on board, visit public areas of the vessel, and inspect documents. Cf. United States v. Brignoni-Ponce, 422 U. S., at 880. “Neither the [vessel] nor its occupants are searched, and visual inspection of the [vessel] is limited to what can be seen without a search.” United States v. Martinez-Fuerte, supra, at 558. Any interference with interests protected by the Fourth Amendment is, of course, intrusive to some degree. But in this case, the interference created only a modest intrusion.
We briefly recapitulate the reasons, set forth above in greater detail, which lead us to conclude that the Government’s boarding of the Henry Morgan II did not violate the Fourth Amendment. In a lineal ancestor to the statute at issue here the First Congress clearly authorized the sus-picionless boarding of vessels, reflecting its view that such boardings are not contrary to the Fourth Amendment; this gives the statute before us an impressive historical pedigree. Random stops without any articulable suspicion of vehicles away from the border are not permissible under the Fourth Amendment, United States v. Brignoni-Ponce, supra; Dela*593ware v. Prouse, 440 U. S. 648 (1979), but stops at fixed checkpoints or at roadblocks are. Ibid. The nature of waterborne commerce in waters providing ready access to the open sea is sufficiently different from the nature of vehicular traffic on highways as to make possible alternatives to the sort of “stop” made in this case less likely to accomplish the obviously essential governmental purposes involved. The system of prescribed outward markings used by States for vehicle registration is also significantly different from the system of external markings on vessels, and the extent and type of documentation required by federal law is a good deal more variable and more complex than are the state vehicle registration laws. The nature of the governmental interest in assuring compliance with documentation requirements, particularly in waters where the need to deter or apprehend smugglers is great, is substantial; the type of intrusion made in this case, while not minimal, is limited.
All of these factors lead us to conclude that the action of the customs officers in stopping and boarding the Henry Morgan II was “reasonable,” and was therefore consistent with the Fourth Amendment. The judgment of the Court of Appeals is
Reversed.
See also 46 U. S. C. § 277 (provides similar authority for “[a]ny officer concerned in the collection of the revenue”). Cf. 14 U. S. C. § 89(a); 19 U. S. C. § 1581(b).
Section 1581(a) provides customs officials with authority beyond boarding for document inspections. In this case, however, we are concerned only with the more narrow issue.
Respondents briefly argue that we should not reach even this question. Relying on United States v. Sarmiento-Rozo, 592 F. 2d 1318 (CA5 1979), respondents contend that this case is moot because they have been deported and, subsequent to the issuance of the mandate by the Court of Appeals reversing their convictions, the indictments against them were dismissed. Sarmiento-Rozo provides some authority for respondents’ argument; nevertheless, we reject the contention.
The Government has sought review of the Court of Appeals’ decision reversing respondents’ convictions. Ordinarily our reversal of that decision would reinstate the judgment of conviction and the sentence entered by the District Court. See United States v. Morrison, 429 U. S. 1, 3 (1976) (per curiam). The fact that the Government did not obtain a stay, thus permitting issuance of the mandate of the Court of Appeals, would not change the effect of our reversal. See Aetna Casualty & Surety Co. v. Flowers, 330 U. S. 464, 467 (1947); Carr v. Zaja, 283 U. S. 52 (1931). Under our reasoning in Mancusi v. Stubbs, 408 U. S. 204, 205-207 (1972), the absence of an indictment does not require a contrary conclusion. Further, it is settled law that the preliminary steps in a criminal proceeding are “merged” into a sentence once the defendant is convicted and sentenced. See Parr v. United States, 351 U. S. 513, 518-519 (1956); Berman v. United States, 302 U. S. 211 (1937). Upon respondents’ conviction and sentence, the indictment that was returned against them was merged into their convictions and sentences, thus making unnecessary a separate reinstatement of the original indictment.
That respondents have been deported likewise does not remove the controversy involved. Following a reversal of the Court of Appeals, there would be a possibility that respondents could be extradited and imprisoned for their crimes, or if respondents manage to re-enter this country on their own they would be subject to arrest and imprisonment for these convictions. See United States v. Campos-Serrano, 404 U. S. 293, 294, n. 2 (1971). In addition, as a collateral consequence of the convictions, the Government could bar any attempt by respondents to voluntarily re-enter this country. 8 U. S. C. § 1182(a)(9). See Pennsylvania v. Mimms, 434 U. S. 106, 108, n. 3 (1977) (per curiam); Sibron v. New York, 392 U. S. 40, 53-57 (1968).
*582The dissent’s discussion of mootness places heavy reliance on this Court’s decision in Ex parte Bain, 121 U. S. 1 (1887), and a hypothetical example in a civil proceeding between Peter and David. Post, at 594-598, and n. 1. Ex parte Bain was long ago limited to its facts by Salinger v. United States, 272 U. S. 542 (1926), where the Court said:
“In the case of Ex parte Bain, 121 U. S. 1, on which the accused relies, there was an actual amendment or alteration of the indictment to avoid an adverse ruling on demurrer, and the trial was on the amended charge without a resubmission to a grand jury. The principle on which the decision proceeded is not broader than the situation to which it was applied.” Id., at 549 (emphasis added).
In the present case, there is no doubt whatever that a valid indictment was returned by the grand jury, the case was tried on that indictment, and, unlike the dissent's hypothetical civil analogy, a judgment pursuant to Federal Rule of Criminal Procedure 32 was entered on the jury verdict of guilty. At this juncture, for reasons explained above, the indictment vvas merged into the judgment, and a successful effort on the part of the Government to reverse the judgment of the Court of Appeals would have the effect of reinstating the judgment of conviction.
There is no issue in this case concerning the activities of the officers once they boarded the Henry Morgan II. The only question presented to this Court concerns the validity of the suspicionless boarding of the vessel for a document inspection.
Respondents, however, contend in the alternative that because the customs officers were accompanied by a Louisiana state policeman, and were following an informant’s tip that a vessel in the ship channel was thought to be carrying marihuana, they may not rely on the statute authorizing boarding for inspection of the vessel's documentation. This line of reasoning was rejected in a similar situation in Scott v. United States, 436 U. S. 128, 135-139 (1978), and we again reject it. Acceptance of respondents’ argument would lead to the incongruous result criticized by Judge Campbell in his opinion in United States v. Arra, 630 F. 2d 836, 846 (CA1 1980): “We would see little logic in sanctioning such examinations of ordinary, unsus-pect vessels but forbidding them in the case of suspected smugglers.”
Relying on the words “bound to the United States” in the 1790 statute and this Court’s decision in Maul v. United States, 274 U. S. 501 (1927), the dissent contends that the Act of Aug. 4, 1790, § 31,1 Stat. 164, did not grant any authority to board a vessel found in domestic waters. Post, at 600-601, n. 7. The dissent misreads the statute and the Maul decision. As noted, § 31 of the 1790 Act provides for the boarding of vessels found “in any part of the United States, or within four leagues of the coast thereof, if bound to the United States.” (Emphasis supplied.) The dissent completely ignores that part of the statute which reads “in any part of the United States.” Furthermore, the phrase “if bound to the United States” obviously qualifies only the phrase “within four leagues of the coast.” It would make no sense whatsoever to say that the statute authorizes the boarding of vessels found in “any part of the United States” only so long as such vessels are “bound to the United States.” The dissent also says that because § 48 of the Act of Aug. 4,1790, authorized some searches without regard to location, it must be read as the only provision in the Act that allows boardings in domestic waters. Post, at 600-601, n. 7. Again the dissent misreads the statutory scheme. Section 48 expressly applies only to seizures of “goods, wares or merchandise subject to duty” and *586thought to be concealed on “any ship or vessel” or “any particular dwelling-house, store, building or other place.” Unlike § 31, § 48 does not purport to deal with boardings for inspection of documents. In short, the two sections are concerned with different matters and nothing in one can be read to limit the other.
The dissent’s reliance on the concurring opinion of Justice Brandéis in Maul seriously misreads that concurrence. Where the dissent says that the concurrence “recognized” that it was only in 1922 that Congress purported to authorize suspicionless boardings of vessels not “bound to the United States,” the dissent’s reading of Justice Brandéis’ language is imprecise, to say the least. Observing that the 1922 amendments made two changes in the statutory law, he described one of them in these terms: “Unlike the earlier statutes, it did not limit to inbound vessels the right to board and search.” 274 U. S., at 529. Thus Congress in 1922 allowed searches to be made within four leagues of the coast of any vessel, whether inbound or not. But this change in no way altered the separate provision in the same sentence of the 1922 statute retaining the authority to “go on board of any vessel or vehicle at any place in the United States
Nor is anything in the Court’s opinion in Maul to the contrary. The Court was asked to decide whether the Coast Guard was authorized to seize an American vessel “on the high seas more than twelve miles from the coast.” Id., at 503. In tracing the history of statutory authorization for “seizures made on the high seas,” id., at 504, the Court properly noted that when acting pursuant to the Act of Aug. 4, 1790, and its pre-1922 descendants, such seizures were authorized only for inbound vessels within the 12-mile limit, id., at 505-506. The Court determined, however, that the Act of Mar. 2, 1799, § 70,1 Stat. 678, authorized the seizure of American vessels beyond the 12-mile limit where the Coast Guard was acting pursuant to “any [law] respecting the revenue.” Nothing in the Maul decision even remotely purported to apply to the boarding of vessels in domestic waters.
The dissent maintains that in lieu of the type of stop made in this case, it would be possible to enforce documentation laws by requiring vessels to *592display identification markings more similar to automobile “license plates” and for the Coast Guard to maintain extensive records on shore that can be referred to by radio. Even assuming that these alternatives are feasible, Congress has chosen a different method. So long as the method chosen by Congress is constitutional, then it matters not that alternative methods exist. Cf. Cady v. Dombrowski, 413 U. S. 433, 447 (1973).
Respondents suggest that even if the public interest is great in stopping commercial vessels, it is not so with “pleasure boats.” The difficulties with such line-drawing are exemplified by this case. Respondents assert that they were in a “pleasure boat,” yet they proved to be involved in a highly lucrative commercial trade.