Once such unenforceable laws are on the books, there are serious negative consequences, including:
1) Selective enforcement
The federal authorities may try to make an example of a few high-profile cases, but that will probably anger the other gun owners more, rather than cow them. (For more on the problems of proliferation of laws which prosecutors can then selectively enforce, see this paper by law professor Glenn Reynolds.)
2) Diversion of limited police resources from real crimes
This is just another example of Charles de Montesquieu’s adage: “Useless laws weaken necessary laws.”
3) Increasing contempt by otherwise honest citizens for the central government
As Reynolds noted in a separate USA Today piece, Americans are increasingly mistrustful of the government. New gun laws would worsen this problem.
No one can know exactly how this will play out. This will depend on how strongly the central authorities wish to enforce the law in the teeth of the defiance, and how committed gun-rights supporters are to sustained civil disobedience. If history is any guide, violence is not out of the question, even if cooler heads on both sides do not wish it. New gun laws could be the political equivalent of a spark thrown onto dry tinder.
According to Politico, gun control is the most divisive issue separating the two major political parties. Passing the law would accelerate the already growing polarization of America.
During Obama’s first term, many on the Left who were frustrated by their inability to fully impose their political agendas repeatedly invoked the mantra that America was “ungovernable.” If the president’s gun-control proposals become law, they haven’t seen anything yet.