Stop sending money to states that allow (or tolerate) the hiring of illegal aliens. CO had on their books (until 2008, when they elected a democrat for a governor) a law that was very clear and straightforward, Hire/rent to/give aid to an illegal, and you go to jail and pay a fine. This meant no money, no housing and no welfare/food stamps/WIC/unemployment. When this law went into effect, the interstates were jammed with illegals fleeing the state.
This would save millions in federal enforcement, and make the decision to be a safe haven for illegals cost the state billions in federal funds AND open/create millions of jobs!