That's true, but the blanket ban on felons having the RKBA may not be proper due process, on two counts. First it may be that the removal of rights must be as part of the individual trial and sentence. Secondly, and related, is the "retroactive" nature of the "punishment". That is, people whose felony convictions predate the law banning felons from possessing firearms may have a good argument that it is an ex post facto law.
I didn't say I agreed with the policy, only what the Constitution states. Used to be, Sheriff let you out of the pokey, you got your six guns back. Of course, more good guys were "allowed" to ventilate the bad guys back then as well.