On July 16, 1969 — the same day Apollo 11 departed for the moon — the “Extraterrestrial Exposure Law” (C.F.R. Title 14, Section 1211) was adopted. This law was in response to concerns about contamination that could endanger human life as a result of contact with little green men, their ships, or anything that “touched directly or came within the atmospheric envelope of any other celestial body.”
The law did not criminalize reaching out and touching E.T. or his ship, but it did require the person who made contact with anything related to a NASA manned or unmanned space mission to be quarantined at the discretion of a NASA quarantine officer. Failure to comply with the quarantine requirements could subject the offender to a $5,000 fine, a year of imprisonment, or both.
The law was repealed in 1991 upon a finding by NASA that it had “served its purpose” and was “no longer in keeping with current policy.”
Still, it would probably be a good idea if you wash your hands after handling anything that has been in space — alien or otherwise.