Should the Department of Homeland Security be able to use Social Security records to crack down on illegal hiring? The department issued a new rule allowing it to do so; labor unions filed suit. A preliminary injunction, issued by a judge in October, means D.H.S. is stymied for now. No trial date has been set.

THE PLAYERS

A.F.L.-C.I.O.Strange bedfellows: The A.F.L.-C.I.O., the American Civil Liberties Union, and the U.S. Chamber of Commerce are on the same side.

ChertoffThe Department of Homeland Security, headed by Michael Chertoff, and the Social Security Administration are on the other side.

THE POSITIONS

A.F.L.-C.I.O.Unions and business groups agree that to implement the rule would be onerous and expensive—close to $100 million.

ChertoffEmployers need to vet their workers. For each illegal immigrant hired, the employer should pay a $2,000 fine.

THE CONCERNS

A.F.L.-C.I.O.The A.F.L.-C.I.O. worries that employers will fire workers rather than risk a fight with the government.

ChertoffWithout the rule, D.H.S. won't be able to weed out immigration scofflaws.

THE LEGALITIES

A.F.L.-C.I.O.Homeland Security doesn't have the legal authority to change Social Security regulations.

ChertoffPart of Homeland Security's job is to enforce immigration laws—and to create new rules that further the cause.

THE NUMBERS

A.F.L.-C.I.O.More than 8 million people could be affected if D.H.S. gets its way. That's about 5 percent of the working population.

ChertoffMore than 4,300 people were arrested by D.H.S. for work-related immigration violations in 2006, up from 510 in 2002.

THE IMPLICATIONS

A win for Homeland Security might tempt companies to pay workers off the books. A win for the A.F.L.-C.I.O. might embolden employers who hire illegal labor.

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