The Migratory Bird Treaty Act is very interesting from a legal standpoint. Regulating wild birds is not one of the enumerated powers of Congress, but the federal government entered a treaty with Canada to protect migratory birds and successfully argued in the Supreme Court that it could enter such a treaty despite not having the power to enforce it, and that by entering the treaty it gained the power to enforce it. This is vaguely reminiscent of the Five Eyes reciprocal spying arrangement.
During the 1930s there were some other interesting attempts at regulating things through complicated "taxation" systems, including marijuana and machine-guns (only the latter law survives today).
Creative legislative techniques like this don't seem to occur as often now that Congress has settled on just declaring everything to be "interstate commerce" (which is how the modern drug laws work, and if a migratory bird law were passed today I'm sure they would consider birds that cross state lines to be involved in interstate commerce).
For anyone curious, here are the birds in the US covered by the Migratory Bird Treat Act [1]. A good first approximation is that if you see a wild bird, and it is not a European Starling, House Sparrow, Pigeon, or a bird that you can get a hunting license for, it is probably covered.
There are some curious state laws regarding birds. For instance, California Penal Code, § 598:
> Every person who, within any public cemetery or burying ground, kills, wounds, or traps any bird, or destroys any bird's nest other than swallows' nests, or removes any eggs or young birds from any nest, is guilty of a misdemeanor.
During the 1930s there were some other interesting attempts at regulating things through complicated "taxation" systems, including marijuana and machine-guns (only the latter law survives today).
Creative legislative techniques like this don't seem to occur as often now that Congress has settled on just declaring everything to be "interstate commerce" (which is how the modern drug laws work, and if a migratory bird law were passed today I'm sure they would consider birds that cross state lines to be involved in interstate commerce).