The American Civil Liberties Union is complaining about what it calls a “Constitution-free zone” — a 100-mile-wide area along America’s land and coastal borders where authorities can stop, search, and detain anyone for any reason.

Customs and Border Patrol, a component of the Department of Homeland Security, was authorized by Congress to operate within a “reasonable” distance of the borders, and the ACLU says that distance has been set at 100 miles in regulations governing the CBP.

According to the ACLU, nearly two-thirds of the U.S. population lives within 100 miles of the borders and coasts, and the zone includes many major metropolises.

“Part of what we’re trying to do is to draw our own line in the sand here and say this has to stop,” said Barry Steinhardt, director of the ACLU’s Technology and Liberty Program.

“We cannot determine two-thirds of America as a Constitution-free zone.”

Homeland Security has set up several dozen checkpoints within the zone. When citizens or visa holders reach a checkpoint, most are waived on after showing identification. But if agents suspect the person is in the country illegally, they can detain the individual until an investigation is completed, the Web site, Wired Web, reports.

“It is a classic example of law enforcement powers expanding far beyond their proper boundaries — in this case, literally,” said Caroline Fredrickson, head of the ACLU’s Washington Legislative Office.

Homeland Security spokesman Jason Ciliberti said the checkpoints follow rules established by the Supreme Court, which “has determined that brief investigative encounters do not constitute a search or seizure.”

According to the Raw Story Web site, the ACLU has not yet filed lawsuits, but the organization says its lawyers in border states are preparing cases.