Once again, the states are rebelling against Washington. Fed up with dithering in D.C., states are proving enforcement works. Enforcement not only can prevent illegal immigration, but actually reverse it.

Illegal immigrants by the tens of thousands are leaving states that have adopted tough new laws - Colorado, Georgia, Arizona and now Oklahoma. Local efforts are being launched too quickly to count, involving more than 100 communities so far.

When denied jobs or public benefits, many illegals return to Mexico. Others move within the United States to areas with local amnesty policies. That migration may spark a new outcry from citizens in amnesty cities.

Left-leaning groups are on the move, too, flocking to the courts in efforts to block state and local enforcement. Only Congress is standing still - except for back-sliding efforts to push more back-door amnesty.

Details of state and local laws vary, but the impact is consistent. Typically, they deny public benefits to illegal immigrants and try to make sure employers don't hire them.

Oklahoma's law kicks in soon - Nov. 1 - and Hispanic leaders claim 25,000 illegals have already departed the Sooner State. Businesses that catered to them say their sales are down 20 percent. They're backing a lawsuit challenging the new crackdown.

But the crackdown is a gain for taxpayers. Estimates show illegal immigrants cost Oklahoma taxpayers $200 million a year, mostly for education and health care.

Arizona's new employer sanctions don't start until Jan. 1. A half-million undocumented people supposedly await the outcome of court challenges, but the Arizona Republic still reports the outmigration already tops 100 per day.

Due to Georgia's new law, businesses with an illegal alien customer base have seen sales drop as much as 40 percent. And money wired from Georgia to Mexico and Central America declined. Similar sales drops are reported elsewhere.

Colorado supplemented its new laws with a special detachment of state troopers. An Aug. 31 report to the governor said the first month's results "exceed anyone's expectations," catching 150 illegal immigrants plus those who smuggle them.

State legislators this year introduced some 1,400 immigrant-related bills, and 182 became law. Local ordinances were proposed or adopted in 104 cities and counties.

Bucking the trend is Illinois, which passed a law prohibiting employers from using a federal database to screen out illegal immigrants. That's where the litigation trend cuts both ways: The Department of Homeland Security is suing Illinois to force it to comply, saying they can't pick and choose which federal laws to obey.

Ironically, Washington spent years picking and choosing when federal enforcement would have prevented today's epidemic problem. Current federal enforcement remains limited, focused on illegals who have committed violent crimes but not on illegal immigration generally. So-called sanctuary/amnesty cities are clearly violating federal law, as New York City learned from a U.S. Supreme Court ruling in 2000. It's time for the feds to use that precedent and take other cities and state scofflaws to court.

In Congress, the Democrat majority and some Republicans still push back-door amnesty. Sen. Dianne Feinstein, California Democrat, proposed amnesty for almost 2 million illegal farm workers to pick crops. Sen. Richard Durbin, Illinois Democrat, used children as bait for amnesty, proposing in-state college tuition and federal financial aid to children of illegal immigrants - and letting them and their parents stay in America. Mr. Durbin calls it the "DREAM Act." The Heritage Foundation's Kris Kobach properly calls it "a nightmare."

The battleground is swiftly shifting into court, where activist judges are eager to side with border violators. One judge blocked federal officials from notifying millions of employers that their workers may be using false Social Security numbers. Hazleton, Pa., had its local ordinance struck down. More lawsuits are pending. Enforcement works, but liberals want it stifled before people realize that.

The big claim is that immigration is solely a federal issue. If activist judges block state and local enforcement, the public reaction could rival the anger over decisions about abortion and forced busing. But there's a difference this time: Those controversial rulings claimed that the Constitution barred action by any level of government. Immigration rulings would have the side-effect of confirming that Washington has the ability to act. Congress isn't helpless - just hopeless.

By demonstrating that enforcement works, state and local governments are clarifying the issues, and tens of thousands of illegal immigrants are self-deporting. The public outcry that defeated the amnesty bill this spring has found a new outlet, keeping the heat on Washington all the way into the 2008 elections.

Ernest Istook is a distinguished fellow in Government Relations.