EDITORIAL BORDER CONTROL ENFORCEMENT IS A KEY COMPONENT OF IMMIGRATION REFORM.

FROM the U.S.-Mexico border in Arizona comes an important reminder for federal lawmakers: Law enforcement works.

We realize this is hardly stunning news, but it may as well be, given Washington's decades-long refusal to secure the border. Finally, President George W. Bush has dispatched a small contingent of National Guard troops, and the results have been significant and immediate.

In the first 10 days of June, the presence of 55 Guardsmen -- who only serve in a support capacity -- has brought about a 23 percent reduction in detentions at the border.

Some of the change may owe itself to the hot summer, but a decline this steep is unusual. Clearly the mere presence of the troops has been enough to discourage many illegal immigrants from crossing the border -- at least in Arizona, anyway.

This is the same phenomenon that explains why we all slow down when we see a cop on the freeway, or why street violence drops where officers regularly walk the beat. Serious, visible law enforcement is key to solving the nation's immigration mess.

That's not to say enforcement alone is the answer -- just because detentions in Arizona have dropped hardly means illegal crossings have stopped -- but clearly it is a key component of a comprehensive reform plan. So is facilitating more orderly legal immigration and bringing some 12 million illegal immigrants out of the shadows.

The presence of National Guard troops seems to have been a successful first step toward reforming American immigration. But there's still much more work to do.