Could you show me..in the constitution, where the federal government has the authority for immigration?
They have the authority for naturalization, but, I believe it is the states who are to determine immigration.
It is simply a guess of what five liberal justices on the SCOTUS would do.
This link breaks down the legal history of the Federal basis for Immigration law:
http://www1.umn.edu/humanrts/immigrationlaw/chapter2.html