 After both agents shoot down the alien ship near the end of the  film, K arrests the alien, citing his violation of the "Tycho  Treaty". Tycho was the crater on the Moon (named after 16th century  Danish astronomer, Tycho Brahe (who had a false nose made of a  copper alloy, incidentally)) where the monolith was found in  _2001: A Space Odyssey (1968)_ (qv).