Romney generally took a hard-line approach to illegal immigration. He spoke out against the comprehensive immigration reform bill that stalled in Senate (NYT) in June 2007, calling it "a form of amnesty." (ABC)

Romney says the United States should implement an "enforceable employer verification system" using biometrically-enabled identification cards (PDF) for non-citizens. On the Bill O'Reilly Show in 2006, Romney said, “you have to have a tamper-proof document  to make sure that people who are here [and] are aliens are identified and registered, and people cannot hire them unless they're here legally.”

As the governor of Massachusetts, Romney received Washington's approval to allow state troopers to enforce federal immigration law (BosGlobe) and arrest illegal immigrants.