The domestic violence statute is certainly not Constitutional under several criteria.
The most blatant, though it wouldn't set any precedent for RKBA is that it was retroactive in its effects. Someone convicted in 1970 still lost their rights when it was passed.
This effected a lot more people than one would expect, and was most notable with many police, military, and various forms of security that had to have firearms for their career.
Many people associate domestic violence with "wife beaters". But the truth is, especially before Lautenberg passed this legislation, that a lot of people in messy divorces or with spousal problems had plead guilty to petty charges just to be done with a situation and move on.
Even many who had not done what was accused, when offered some deal like a couple days community service accepted.
It didn't remove your rights before it retroactively did in 1996, and some considered it a small price to pay prior. Even today many non-gun owners are not aware they can lose their rights over it, so many not fight it with thousands of dollars and refuse to take any deals, and then find out later they have no gun rights.
The other thing is
what can count as domestic violence is very petty, in no way needing to approach "wife beating". Just getting in each others' face in what is considered an intimidating manner can be an "assault".
No contact is necessary for an assault.
Even a battery can be very petty: Wife or girlfriend has a tantrum and starts breaking things and you grab her wrists and she yanks away or tries to go back to breaking things or even hitting you?
Well to hold on would take a relatively tight grip, the kind of grip that can easily bruise a woman (women bruise much easier than men because their higher ratio of body fat makes blood vessels less elastic and susceptible to breakage, just look at most female athletes they are covered in bruises the men who do similar things are not.)
That will readily be a battery charge, resulting in charges if the police show up. Even if it is just because a neighbor calls after hearing the argument, which was over 5 minutes later, and both spouses were working out the issue.
Or a women slapping a man, that is an actual strike, and obviously certainly a battery.
Yet Hollywood taught a whole generation of women that the right thing to do when your honor is insulted by a man is give them an open handed slap across the face.
Lifetime prohibition.
Or the drink in the face, yet another battery, yet it is another thing women who are insulted have been taught to do in some circles.
Lifetime prohibition if charged.
Then of course you have the blatant lies. Men and women are known to claim all sorts of lies or exaggerations in divorces, or custody battles. Or set up or frame the other to gain some sort of leverage. Some bitter towards the other for years.
Anyone can claim an unrelated mark, or bruise was put there by a spouse. Or even intentionally make a new one (knew a girl that actually hit herself in the face to get her boyfriend in trouble after he cheated on her.)
Now about being Constitutional outside of the retroactive aspect? It certainly would appear the permanent removal of the rights of someone "free" in society was against the intent of the founders.
However if removal of the rights of any felon is valid...(and there is some really petty felonies too, including some things people wouldn't even know was a crime. Along with some that are non-violent but obvious crimes, and then of the course the serious violent ones.)
Congress in 1968 decided that felons would be prohibited. If that is valid then why would Congress prohibiting all domestic violence convictions not be?
What about all misdemeanors period? Or maybe more than 3 traffic tickets in 5 years? (That habitual traffic violator who has demonstrated they cannot be trusted in society with several tons of transportation, so certainly could be even more dangerous or irresponsible with a weapon!
)
Congress made the law in 1996, just as they made the one in 1968. If Congress can remove rights, then why couldn't Congress continue to remove rights for additional offenses?