KEENE, N.H., and WASHINGTON -- In 2007, Mitt Romney ran a radio ad hitting New York (when former Mayor Rudy Giuliani was running), Newark, NJ, and San Franscisco for being “sanctuary cities” for illegal immigrants.

At an event in Keene, NH, Romney was asked about “sanctuary cities” and what he would do about them if president.

It’s an issue he could try to use against Texas Gov. Rick Perry. Pew found that Texas has the second-highest number of illegal immigrants in the country -- 1.7 million, second only to California

“As you know, I opposed sanctuary cities as the governor of my state,” Romney said. “And the idea that a city would determine that it's not going to follow the U.S. law is unacceptable and immigration law is federal law.

“Immigration laws are the responsibility of the federal government. The fact that you're seeing states come up with various programs to try and secure their border is simply an indication that the federal government has failed in doing its job. And I need some lawyers to tell me how to go about doing it, but I would end sanctuary cities, if it's legally possible.”

In at least 2005, however, Boston was identified as a “sanctuary city” for illegal immigrants by a former lawyer for the United States Immigration and Naturalization Service. And the Giuliani campaign criticized Romney in 2007 for not doing anything about Cambridge, Somerville and Orleans -- three cities in Massachusetts, “which to varying degrees had declared themselves sanctuaries for illegal immigrants,” the Globe wrote.

"Why should the American people believe Governor Romney has the right kind of executive experience for America when he claims he was powerless to take action against the three sanctuary cities in Massachusetts who refused to enforce illegal immigration laws?” a Giuliani campaign statement read at the time. “If there were 'statutes' or 'formulas' standing in Romney's way, then why didn't he take action to change them?"

The Romney campaign in 2007 pointed to an agreement Romney signed “with the federal government to deputize state troopers to enforce immigration laws in Massachusetts….”

But the Globe noted: "As governor, Romney never directly addressed the issue of sanctuary cities. His strongest stand on illegal immigration resulted in a successful veto of tuition discounts at state colleges for illegal immigrants.”

And: “That state trooper initiative, signed by Romney three weeks before leaving office, was largely ridiculed as grandstanding by critics who said he was burnishing his conservative credentials for a presidential run.”

Video shot by NBC's Garrett Haake; Edited by Natalie Cucchiara