It occurred to me recently that no country on Earth currently has a law against killing any sentient alien life forms that might come to visit us.
Now, call me overcautious but I wouldn't want to visit a place where it would be perfectly legal for anyone to kill me.
Perhaps the reason that we have not been visited by extra-terrestrials is simply that they think Earth would be a dangerous place for them.
Perhaps all we need to do to join the interstellar community is to pass a law affording the same rights that humans have to any aliens that might visit us.