Demjanjuk's legal troubles began in 1977, when the government initiated a proceeding to denaturalize him.
From the time.com
She persuaded Congress to pass legislation in 1978 to denaturalize and deport participants in wartime persecution.
From the freep.com
Austria passed a similar law in 1933 by which it could denaturalize any citizen who participated in a hostile action against the state.
From the en.wikipedia.org
More examples
Make less natural or unnatural
Strip of the rights and duties of citizenship; "The former Nazi was denaturalized"
(Denaturalized) Naturalization (or naturalisation) is the acquisition of citizenship and nationality by somebody who was not a citizen or national of that country when he or she was born.