Firstly; that would be a Federal problem, not something that the City can do anything about. Secondly; even if they were illegal immigrants (which is undetermined at this point; most of them claim asylum and have had no determination made for their case) they would still have had the right to shelter under City law.
I'm saying that the arrival of a large number of people, who are legally unable to work, and who have no support system from families, and whom the City is legally obliged to house is a problem.