In an alternate timeline, the Extradition Acts were a series of laws enacted by the Parliament of United Earth and its majority Isolationist Party in 2161, which expelled all non-Terrans from Earth. These Acts did not forsee the possibliity of a human marrying an alien, however, allowing T'Pol to remain on the planet following her marriage to Trip Tucker. (Star Trek: Myriad Universes novel: A Less Perfect Union)