It has happened to me in the past though to accidentally own past governmental websites.
For example, I used to own a domain which used to belong to india's main governmental insurance.
As soon as I realised that I owned something that could lead into problems, I deleted the domain (or let it drop without any nameservers on... don't remember exactly).
The question the OP poses is an interesting one though,
could I have sold such a domain back to the government or maybe make an attempt?