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The nation's first homeland security secretary said Tuesday that critics of immigration reform need to "get over it," and warned that Americans shouldn't be so "arrogant" as to believe that "everybody that comes across the border wants to be an American citizen."

Speaking at Georgetown University to celebrate the eight anniversary of the U.S. Department of Homeland Security, former secretary Tom Ridge said he hopes "sometime in the future" the U.S. government takes a serious look at immigration policy "in general," even though “it's the third rail of contemporary politics right now."

"At some point in time you've got to say to yourself, 'We're not sending 12 million people home,'” the former Republican governor of Pennsylvania said. “Let's get over it. ... We're not going to send them home, so let's just figure out a way to legitimize their status, create a new system, and I think that will add more to border security than any number of fences we can put across the border."

Many in the crowd erupted in applause.

Ridge offered two key steps for immigration reform, the first being, "Don't think that everybody that comes across the border wants to be an American citizen."

"I don’t think you should be that arrogant," he said. "A lot of them just want to come up here to work lawfully and go back home." Ridge's successor, Michael Chertoff, offered similar sentiments, saying "most people who come across the border are not coming to do harm to the us, they're coming across the border for jobs."

Ridge also suggested using biometrics to document workers inside the United States, "building a database" that employers can use to check the status of potential employees, and engaging in "strong enforcement" against employers who hire illegal immigrants.

Ridge indicated frustration with the fact that, while in Congress under President Ronald Reagan, he was criticized for supporting "amnesty" -- using the term in a way that mocked his critics on the issue. He said "at some point" Congress has to accept responsibility for issues surrounding illegal immigration and border security.

Current Homeland Security Secretary Janet Napolitano, who joined Ridge and Chertoff on the Georgetown University panel, called illegal immigration and border security a "key struggle" and "key issue" for her department.

"The border with Mexico is something that we've focused on quite a bit," she said. "It's an area where we're assisting [Mexican] President Calderon in his very valiant war against these large and very powerful drug cartels that exist over the bridge from El Paso, over the road from Laredo, across basically a huge gully in Nogales."

Chertoff urged the public to have "realistic" expectations when it comes to border security.

"The idea that there's a capability to pinpoint every single threat -- even at the granular level -- is not realistic," he said. But, he said, "layers" of security, "intelligence about who comes and goes," and "the assets on the border" give authorities "a reasonable chance of intersecting and apprehending" threats.

"And the truth is, it has worked," Chertoff said. "There has been over the last several years a drop in the number of people who come into the country illegally between the ports of entry. That's something that is attributable to the economy, but frankly some of it is attributable to enforcement," dating back to the Bush administration.

"You can -- depending on where you are on the border -- use a series of tools in a way that minimizes the flow," he said. "Is it going to be an absolute seal? No. but will it [curtail] the risk in conjunction with these other tools? Yes it will."