Yes, it's strange that when "they" do it, it's legal, and when "we" do it, it's illegal. However, we should not forget that they sit in a position of power and can do things that are essentially bad, but they will always present their moves as justified for any reason, say the protection of national security.
As for the return of seized coins, I think that this happens very rarely, because the process of proving that someone owes something to someone is certainly not an easy or quick process. In the documentary about the Centra Tech scam, it was mentioned that the authorities seized a certain amount of coins, but also that none of the victims received anything in the years after that.