The expression 'gun buy-back' as used by Kamala Harris and other leftists makes no sense. If I sell you something, I am free to attempt to buy it back from you, and you are free to refuse to sell it to me. But I didn't buy my guns from the government, but from reputable gun dealers in compliance with all the Federal and state and local regulations. So the government can't buy them back from me. That is ruled out by the very sense of 'gun buy back.'
Furthermore, if the dealer wants to buy back my gun, I am free to say No. But I am not free (in the same sense) to say No to the government when they try to confiscate my firearms.
'Federal gun buy-back' is an obfuscatory phrase designed to confuse and trick the populace. In plain English, it amounts to COERCIVE CONFISCATION with monetary compensation.
When I call leftists moral scum, part of what I mean is that they misuse language to trick and confuse people. Decent folk don't do that. They say what they mean, and they mean what they say.
Leftists are stealth ideologues. They don't say what they mean, and what they mean is not what they say.
If they were intellectually honest, that would be one fewer reason for people to buy guns.