In a sane world where the people were in charge of their government, that was once true. But over the decades the congress has offloaded more and more of their traditional regulatory authority to the various bureaucratic agencies of the permanent government. Your real government. Giving their "regulations" the force of law. Want to have some fun? Ask the technical people at the ATF, the ones who are responsible for defining what is and is not a firearm, and what kind it is under the law, if an AR has a receiver. They suddenly become very intersted in their shoes and the ceiling tiles. Because under the black and white letter of the law, it doesn't. And their own people have said so for years. Every time a case has gone to court to settle it once and for all, they drop the case because they know they would lose. This is the same regulatory agency that once said that a piece of string could be legally defined as a machinegun.