Again.

Two years after he fled persecution in Pakistan and carved out a life of freedom in Dallas, he is fleeing the United States and the fear of the FBI coming for him.

"I loved Dallas," Rahim said, standing along a bleak Detroit street with all his possessions stuffed into two large rolling suitcases.

But the fear of being deported back to Pakistan for an immigration violation is too severe for him to risk staying in the United States. He already has spent five days in a Detroit jail, housed with criminals because he showed up at the wrong immigration counter in Canada by mistake and was turned back to America, where immigration officials held him because of his expired visa.

Rahim is among thousands of immigrants who have left the United States in the past year after coming here in search of better and safer lives. Some had expired visas. Others were in the United States legally but feared deportation to their home countries if they registered under new, post-9/11 programs.

Many said they left after the government targeted a small segment of the 7 million illegal immigrants in the United States: Muslim and Middle Eastern men.

The face of immigration in America - a nation built by immigrants - is changing dramatically in the shadow of Sept. 11. A string of new policies designed to thwart terrorists instead has entangled thousands of immigrants of all nationalities, many of them here legally.

Arabs and Muslims talk fearfully of FBI visits to their neighborhoods after the attacks, and again before the war with Iraq. Mexican immigrants, both legal and illegal, are afraid to return home because new border restrictions may prevent them from being readmitted to the United States.

Thousands of immigrants lost jobs as airport screeners when non-citizens were banned from holding such positions.

A nation that for years accepted illegal immigration as a reality of American commerce suddenly has shut its gates, and Middle Easterners are being expelled or driven out by the new policies.

Federal officials say the rationale is simple: Immigrants who are violating the law, even in a minor fashion, cannot expect to live in the United States without facing penalty or expulsion.

"There were a lot of people who were flouting our laws," said Dennis Murphy, a spokesman for the U.S. Department of Homeland Security. "They came here as a student, spent a couple of years as a student, and instead of leaving when they were supposed to leave, they decided, 'Well, I'll hang around 'til they catch me.'

"That's not fair to all the people who came here to go through the process, obtain a green card or become citizens, and they go through the process."

The result has been that large numbers of Pakistani and other immigrants have abandoned New York, Detroit and Chicago. In response, advocacy groups have launched legal challenges and public campaigns against a crackdown they say unfairly targets selected immigrant groups.

The exodus includes highly skilled engineers and teachers who have decided to try their chances in Canada, where immigrants seeking refugee status are allowed entry with minimal effort. They are forming new communities and once more learning the ropes of getting their children into school and their paperwork processed so they can get jobs.

But they no longer worry they will end up in jail.

"I'm believing in Canada now; I'm born again," said Abdul Majid Sheikh, a 43-year-old Pakistani who left his Jersey City home and immigrated to Windsor, Ontario, in January.

Before Sept. 11, immigrants who came to the United States on temporary visas routinely stayed even after the visas had expired. There was little enforcement, and federal officials acknowledge that many eventually got their green cards, even after staying in the country illegally.

FBI agents questioned many immigrants in the wake of Sept. 11 and intensified those efforts before the war with Iraq. The bureau tried to convince the targeted communities that these were not sweeps aimed at arresting people, but efforts to seek information on possible terrorist-related activities.

That was a hard sell in many communities, particularly after the federal government decided to require men from 25 mostly Middle Eastern and North African nations to register their presence and submit to being interrogated, fingerprinted and photographed. More than 82,000 male immigrants ages 16 and over who were not green card holders or citizens have complied with the order. More than 13,000 of them now face the possibility of deportation, mostly because of visa violations.

Of those who registered, 136 have been classified as "criminals" by federal officials, and 11 have been detained as suspected terrorists, immigration officials said. The government has refused to divulge their names, nationalities or any information about their alleged terrorist ties.

For many immigrants, both legal and illegal, the requirement triggered the decision to leave for Canada.

Among them are Muhammad Akhtahr-Nazir and his wife, Nasreen, who moved with their two sons from Bayshore, N.Y., to Toronto last December.

The couple had abandoned lucrative careers in Pakistan to move to the United States and hoped to settle in New York, where Nasreen, a 33-year-old artist and school principal, planned to pursue a master's degree in art.

Her husband, a 40-year-old mechanical engineer, had come to New York two months after the Sept. 11 attacks. At the time, his six-month visitor visa had only one month left on it.

By December, his visa had expired, forcing the family to make a choice: stay and risk being deported to Pakistan, or cross over to Canada.

"I should stress, the people of America, there is nothing wrong with the people of America," Nasreen said. "We had so many friends. We discussed the war (in Afghanistan) and politics together with them, but there was no quarreling at all.

"Everything was discussed openly. I cannot say that there was even a single moment where I felt that, 'Oh, my God, where have I come.' "

At one point, the FBI paid the family a visit, asking routine questions about whether they had knowledge of terrorist-related activities.

The matter of the expired visa never came up, and the family debated whether to risk trying to renew it. But as the March 21 registration deadline for Pakistanis loomed, they decided the chance of deportation was too great.

The hardest part was telling their sons, now ages 9 and 6, that they were moving to yet another new country.

"I took a whole night to tell them," Nasreen said. "We left all their belongings in the school. They said, 'Oh, I have left my markers. I have left this and that.' But they are kids."

Today, the four live together in a cramped but neat one-bedroom apartment in a poor section of Toronto.

The targeting of Middle Easterners has outraged civil libertarians and immigration advocates who say the policies are decidedly un-American.

"There are 7 million illegal aliens right here in the U.S.A.," said Samina Faheem, national coordinator of the American Muslim Alliance. "As Muslims, we are not asking for any special favors. We just want to be treated fairly, equally under the Constitution, just like everybody else.

"If they're going to ask 13,000 Muslims to leave the country because they had minor visa violations and they overstayed, then they should deport all of those 7 million people."

Sam Stanton can be reached at sstanton(at)sacbee.com.