One could mitigate that by setting it up where new citizens have a waiting period before they can qualify --kind of like retirement [where you wait till you qualify].  Same for anyone under 18, they [or legal guardians] receive progressively more as the children grow and need more.<p>Or alternatively, your qualification follows you as a natural-born citizen of a given country --so you as a Canadian or American, Japanese, etc., receive UBI from your [original] country no matter where you live or move to so you would never qualify for UBI from a new host country blunting the threat of people thinking new immigrants get a free ride from the new host country.