Title 14, Section 1211 of the Code of Federal Regulations (implemented on July 16, 1969) makes it illegal for U.S. citizens to have any contact with extraterrestrials or their vehicles.
Oh, yea I can see a story based on this. Someone just has to write it PLEASE. Heck you would have to arrest a lot of Metropolis, World Leaders etc. It is just too funny.
Well, good thing Clark and his "vehicle" landed on Earth as early as in 1966, then. Surely it must be legal to have contacts with aliens who were legally adopted and raised by wholesome farmers from Kansas?
If you read the actual reg it only applies to NASA launched stuff and only if you refuse to be quarantined when told to. Published the day the first Apollo moon flight launched.