Heirlooms are important; I don’t think anyone’s possessions that they’ve had for decades should be taken away, nor should collections be broken up. Heirloom also implies that it’s an antique, which is important to consider also.
Take for example someone I knew. This wasn’t exactly an heirloom, but it was “my dad just died and holy crap would you look at this?” There were many things he discovered in a little secret basement enclave, many of which were definitely illegal and probably a war crime to actually use. But I’m going to focus on the mortar right now. It was a nice mortar, great example of the period, and so on. The son (bless him) filled his father’s prized mortar with concrete. Now it still looks great on the outside, but is functionally a paperweight. Heirlooms can be similarly decommissioned, if they’re dangerous enough to warrant it.
You also overlook the genuine need for self-defense in rural areas in which the police can’t get to your property in any helpful time, as well as in cities with terrible police departments and high crime rates like Detroit.
That’s covered under fantasy scenarios.