system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel] To what extent can extraterrestrials legally visit Earth?

Is it ever stated at any point in the MCU what the general opinion is of aliens, and whether they can just visit Earth? 

I know the general public is aware of the existence of aliens in the MCU, and there are certain aliens who clearly are allowed (Thor, Nebula, Rocket) but are there any official government relations with any extraterrestrial species?
gpt
Well S.W.O.R.D. seems to to be holding international authority on behalf of most of humanity's governments.  But they seem to mainly deal on a diplomatic level.

Earth has always been a place someone in a small ship can just drop in on.   Most are dealt with on an individual basis.   Provided they don't try any conquer your world moves or ar e an inherent threat.

It seems they're actually tolerate much better than mutants.