Our government has decided that it is allowed to do all of those things "legally" in certain circumstances. Execution, asset forfeiture, and detainment are all considered "legal". Nothing besides the government is permitted to do these things, they have a monopoly on that right.
You don't need to put scare quotes around words, I'm well aware of the potential legality of all three categories.
Slavery used to be legal too. I'm sorry the government is not completely perfect, but the answer is to go fix it and make things that should not be legal, illegal. Until then it's like complaining about shell companies used by Google and Facebook to avoid paying taxes (a strategy typically well-defended on HN because they're "technically complying with the law").
