United States v. Rybar
United States of America v. Raymond Rybar, Jr., 103 F.3d 273 (3d Cir. 1996), is a case which was argued before the Third Circuit Court of Appeals on September 13, 1995, and decided on December 30, 1996. The appeal addressed the constitutionality of a provision of the Firearm Owners Protection Act of 1986 under the Commerce Clause and the Second Amendment to the United States Constitution.
The case 
Raymond Rybar, Jr., a federally licensed firearms dealer, had conditionally pleaded guilty to two counts of possessing an illegal machine gun under the Firearm Owners Protection Act of 1986. The weapons in question were a Chinese Type 54 7.62-millimeter machine gun (see note below), and a U.S. Military M-3 .45 caliber submachine gun. Rybar was charged with four felonies, but only convicted of two. The other two counts were for failing to purchase a tax stamp (this is not registration) for the machine guns under the National Firearms Act of 1934 for firearms that can not be classified under 18 U.S.C. § 922o. The court ruled in United States v. Rock River Armory (1991), that a conviction under 18 U.S.C. § 922o would violate the fundamental fairness found in the Fifth Amendment. Rybar argued that these convictions violated his Second Amendment rights as well as the commerce clause of the United States Constitution.
The decision 
The Third Circuit Court upheld his convictions 2-1. Authoring a notable dissenting opinion was from then Judge Samuel Alito. Alito argued that the law under which Rybar had been convicted should be vacated, because Congress, in its lawmaking, had not made sufficient findings regarding the impact on interstate commerce clause to fully justify the court deferring to Congressional judgement that the law was authorized by the Commerce Clause. Rather than actually ruling that the law was unconstitutional, Alito asserted simply that Congress had not sufficiently justified it, allowing that, had Congress made sufficient findings, he would defer to those findings.
Error in firearm description 
The case decision mentions a "Chinese Type 54, 7.62-millimeter submachine gun". Such a thing does not exist, and it is probably the result of a confusion between two different Chinese designations. The Chinese Type 54 is a belt fed heavy machine gun of caliber 12.7 x 107 mm, analogous to the .50 BMG M2 Browning machine gun used by American forces. Likely the weapon in question was a Type 56, which is a Chinese copy of the AK-47. This is technically an assault rifle, though the PLA classifies it as a submachine gun. There is also a Chinese Type 56 Carbine, a copy of the SKS, but as the SKS design is only semi-automatic and the AK-47 design is select fire, the AK-47 design would make a far better starting point.