One of the nation's most outspoken law enforcement officers is praising the Trump administration for cracking down on sanctuary cities, slamming liberal politicians for protecting criminal aliens, and explaining what those criminals have done to his community far from the border.

Earlier this week, Attorney General Jeff Sessions announced the Justice Department would lower or eliminate federal grants to locales that fail to cooperate in the enforcement of federal immigration laws.

Milwaukee County, Wisconsin, Sheriff David Clarke is thrilled.

"Finally, we have a president in Donald Trump, who appointed an outstanding attorney general in Jeff Sessions, [and is] unapologetic about immigration enforcement. I am as well," said Clarke, who is also author of the new book, "Cop Under Fire: Moving Beyond Hashtags of Race, Crime and Politics for a Better America."

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After years of lip service from both parties, Clarke says he is happy to see decisive action.

"Finally, we have somebody who's going to get his arms around this thing, along with the Congress. Congress has the constitutional authority to set immigration standards. They're going to have to take the test as well. And you know what? Congress is afraid to deal with this issue because it's explosive," said Clarke.

Despite the warning from Sessions about lost federal funds, mayors and police chiefs around the country say they won't budge. Clarke sees that as a dereliction of duty.

"These mayors out there are abdicating their responsibility to keep their citizens safe. This is nothing more than aiding and abetting criminal activity when you start to harbor criminal illegal aliens," said Clarke.

Opponents of the Trump policy, such as Chicago Mayor Rahm Emanuel and New York City Mayor Bill de Blasio, often stake their positions on America's history of welcoming immigrants seeking a better life, without distinguishing between legal and illegal immigration.

Clarke says that distinction matters.

Hear the interview:

"You got a guy in Donald Trump, the president of the United States, who's actually going to enforce the law. That is a shock to some people. But we're a nation of laws. People want to say we're a nation of immigrants. No, we're not. We are a nation of laws. We are a nation of lawful immigration," said Clarke.

The sheriff also emphasizes that all the mayors and law enforcement officials are being asked to do is deal with criminals who are in the U.S. illegally.

"I'm not talking about immigration in general and not even illegal immigration. I'm not giving it a pass, but I'm focusing on criminal illegal aliens. I think it's a good place to start because these individuals have no business in the country. Many of them have been deported over and over and over again only to return, which shows the border is porous," said Clarke.

Milwaukee, Wisconsin, is nowhere near the southern border, but Clarke says the effects of illegal immigration are having a very real impact on his community.

"We had a case several weeks ago of a criminal illegal alien (with a) criminal history. He was not deported because of the catch and release policies that have gone on," said Clarke.

"In a domestic violence situation, he pointed a firearm at his girlfriend, threatened his girlfriend, pointed a firearm at his two young kids and threatened them as well," said Clarke.

He says that's just one of many crimes and tragedies linked to illegal immigration in Milwaukee County.

"We're talking about murders. We've had criminal illegal aliens involved in drunk driving incidents in Milwaukee County who would have killed other motorists. We've had robberies. We've had sexual assaults. We've had incidents of child abuse," said Clarke.

Unlike officials in sanctuary cities, Clarke says he fully cooperates with Immigration and Customs Enforcement, or ICE, in rooting out criminals in the country illegally.

"I work with ICE and ICE officials have access to all of my booking data. They look at it every day and they decide who they're going to give a further look at. I don't tell them, 'Look at this guy and this guy.' They'll decide and then they'll call and tell us, 'Hold onto this guy or this guy. We want to do some further investigation to see if this person is in the country lawfully,'" said Clarke.

One of Clarke's greatest frustrations is the lack of hard data on criminal illegals. He says it's something liberals deliberately want to keep fuzzy.

"We don't know the extent of the problem because data isn't being collected on crimes involving a criminal illegal alien. It's funny how, in this country, the left demands that we collect data on all traffic stops involving black motorists. We actually collect that data. There's a box you have to check and a form you have to fill out," said Clarke.

"All of a sudden now when we want to collect data, so we have some accuracy as to what's going on with this problem, they don't want anything to do about it," said Clarke, who praises Trump for ordering the collection of data on crimes committed by illegal immigrants.

Clarke is taking steps to prepare his department to offer even more cooperation.

"I'm going to help ICE. I've applied for the 287 (g) program, which, after training, will deputize my law enforcement officers with immigration enforcement," said Clarke.

"We're not going to be doing home raids and we're not going to be doing workplace raids and school raids like the left likes to portray as the sky is falling and the bogeyman propaganda. I'm going to focus on going after criminal illegal aliens, who have been arrested for some very serious crimes, deported previously but got back in," said Clarke.

"Once they get that border sealed, the next time we get them out , we'll be able to keep them out," said Clarke.