I beleive there is a legal obligation to see to the welfare of the people with basic protections. Labor market protections by stemming invasion is legally encumbent upon the federal government.
It's also morally wrong to alter immigration policy just to destroy the labor market for citizens in certain sectors. H1-b visas are immoral in this way.
So you argue that immigration is a crime in the sense that is a moral offense. That's a different context and a different argument. That's fine. But saying that all illegal immigrants are criminals according to the law is not, because they are not.