Actually not. There are planes that are not allowed for domestic consumption. Even if you have the money ($240,000,000) you are not allowed to buy a sukhoi su 25, 27, 34, etc. and the Russians won't sell you one. Even some of the outdated US stuff such as the OV-10D is forbidden to us citizens. You can buy an unarmed YAK from russia, but I understand that they've stopped producing those due to lack of demand.
The point was whether US law would/could prohibit such a purchase, given a manufacturer (such items ARE made domestically) and enough money. As I just noted above, Travolta _does_ own a MiG, and buying & mounting suitable armament is mostly just a matter, again, of money & seller availability.
The challenge was purchase of items in a general category, not specific models thereof which suffer contractual, not legal, restrictions.