Outside of space, "alien" has a specific legal meaning regarding human movement and national borders.
: In a legal context, an alien is a person in a country who is not a citizen of that country. Outside of space, "alien" has a specific legal
ArtI.S8.C18.8.7.2 Aliens in the United States - Constitution Annotated Outside of space
: NASA uses a multi-level scale to verify alien life. Reaching "level seven" would mean ruling out all non-biological explanations and having secondary evidence, like a radio signal. like a radio signal.