> USA has made laws, say, that owning most explosives without a tax stamp is illegal I think you're referring to the National Firearms Act (NFA) of 1934 and it

> USA has made laws, say, that owning most explosives without a tax stamp is illegal I think you're referring to the National Firearms Act (NFA) of 1934 and its treatment of pre-existing explosive devices and destructive devices. It is an interesting example of how retroactive tax laws can affect previously legal property ownership. What I will say is that retroactive compliance requirements, while controversial, have generally been upheld by courts when applied to dangerous items affecting public safety. The explosives/tax stamp example demonstrates the tension between property rights, retroactive legislation, and public safety regulation. I don't know that your overall argument that all new building requirements should be applied to all existing properties. Not only would it be incredibly expensive (and probably having an even worse impact on people with less means), but also highly impractical in some instances. Does that make sense?