"You can have my guns when you ...." Wait. No you can't.
You never have my permission to have them. I would rather my guns go to a drug lord or an inner city gang member after my death than to any government agent.
If you steal them "under color of law" you are a thief and you took them without consent.
If you kill me in the process of stealing them, you are a murderer and my dead silence is not consent.
If you threaten and torture me or my family until you get me to hand them over under duress then you are an aggressor and you deserve the aggressor's fate: death. And in that case I will spend the rest of my life ensuring that your earned fate finds you.
It doesn't matter if there is a "law" saying you have authority to steal my guns. It doesn't matter if you wear a badge or have a title or hold a "high" office. You can never "have" them. Not even if you somehow end up possessing them.