But the categories of people that federal law currently prohibits from possessing or purchasing a gun are overbroad, not reasonably related to the state’s interest in public safety, and raise significant equal protection and due process concerns. Any number of the categories, for example, require no proof of dangerousness, and they often serve to further bias. For example, the list of those barred includes: anyone convicted of a crime punishable by imprisonment for more than a year, whether or not the crime has any connection to violence; people with mental disabilities and many noncitizens who have not been shown to be dangerous in any way; and those who have used substances on the federal controlled substance list, including marijuana in states in which it is legal.Other proposed gun regulations also raise civil liberties concerns. The proposal to ban individuals listed on the No-Fly List from purchasing weapons, for example, is constitutionally problematic, because that list lacks basic due process protections and its standards are unconstitutionally vague.
Source: ACLU (really): https://www.aclu.org/blog/mobilizati...on-gun-control
Another good ACLU article here: http://riaclu.org/news/post/aclu-of-...n-legislation/the ACLU’s analysis expressed concern about “the breadth of this legislation, its impact on civil liberties, and the precedent it sets for the use of coercive measures against individuals not because they are alleged to have committed any crime, but because somebody believes they might, someday, commit one.”
I don't agree with the ACLU's overall stance on the 2nd Amendment, but I think they're moving in the right direction on the "red flag" laws.