WASHINGTON – On the morning of Jan. 28, federal agents knocked on Shirley Tan's door, showed her a deportation letter and put her in handcuffs.

"I was put into a van with two men in yellow jumpsuits and chains and searched like a criminal in a way I have only seen on television and in the movies," said Tan, 44, a housewife and mother from Pacifica.

But Tan is still in the United States today, and she says there's only one reason why: "the great compassion" of California Democratic Sen. Dianne Feinstein.

People seeking to get around U.S. immigration laws have found a good friend in the state's senior senator, who is going to unusual lengths to help her constituents avoid deportation.

Feinstein, a member of the Judiciary Committee, is the Senate's leader in using "private bills" as a way to keep people in the country who otherwise would be forced to leave.

Private bills – narrowly drawn to affect only one person or a few people – are relatively rare. Only 35 are pending in the Senate this year; 14 of them – or 40 percent – bear Feinstein's name. Thirteen of Feinstein's bills date back to previous sessions of Congress but were reintroduced this year.

The bills usually fail because of their narrow appeal, but deportation procedures are oftentimes put on hold when a member of Congress introduces a private bill.

When Feinstein offered a bill on behalf of Tan, her deportation was delayed until 2011.

Feinstein said her private bills are aimed at helping families or individuals who face exceptional circumstances.

"These are people who, if sent back to their home countries, would face enormous hardship," she said. "These individuals have no criminal backgrounds, they're financially secure, they pay their taxes, their children excel in school. They've truly embraced the American dream."

She acknowledged that private relief bills seldom pass, "and many of my colleagues in the Senate have a policy never to introduce them."

But she added: "My staff and I have thoroughly reviewed these cases and believe they merit such extraordinary relief as a private bill."

California's senators take drastically different approaches to private legislation. While Feinstein leads the Senate in private bills, Democrat Barbara Boxer has not introduced a single private bill since joining the Senate in 1993.

"Senator Boxer believes the most effective way to help her constituents is through great casework," said her spokesman, Zachary Coile. "Our caseworkers in California do an exceptional job of helping constituents resolve their problems."

The practice of introducing private bills has always raised questions of special treatment, said Jan Ting, who teaches immigration law at Temple University Law School in Philadelphia and served as assistant commissioner at the Immigration and Naturalization Service in the early 1990s. But whenever a member of Congress took an interest in a case, he said, it prompted an immediate internal review.

"That was enough to put a sticker on the file. Our sense was that, well gosh, we owe it to Congress, who controls our funding, to at least see how the private bill plays out," Ting said.

But he said congressional leaders look disapprovingly at private bills, "as kind of clogging up the works."

"They don't feel that that's how immigration matters should be handled," Ting said. "And if you let too many private bills actually pass, you will then be deluged with private bills."

Only 36 private laws were approved and signed into law from 1995 until 2007, according to the Congressional Research Service In a report to Congress, the research service said private bills "warrant careful consideration" because they're "a special form of relief allowing the circumvention of the public laws" governing immigration.

For many members of Congress, private bills fell out of favor in the 1970s, after Abscam and a series of other corruption scandals involving payoffs for the sponsorship of private bills.

Ting said that private bills then "were thought to be one more manifestation of the fruits of corruption."

Call Rob Hotakainen, McClatchy Washington Bureau, (202) 383-0009.