Boston's politicians, once almost unanimously in support of rigid residency requirements for city workers, are about to get their comeuppance.

Union contracts covering 4,000 of some of Boston's lowest-paid city workers expired eight months ago. This time around, the unions representing those workers, never happy in the first place with the residency requirement, are going to make it a key point in their negotiations.

The reason has to do with an interesting intersection of the 6-year-old residency requirements with Boston's newest political crisis: the high cost of housing.

Boston in the past has kept a tight leash on salary increases, usually limiting them to cost-of-living adjustments of only 3 percent. This time, the city is offering a paltry 2 percent increase.

Yet in recent months the cost of living in Boston, particularly the cost of renting, has soared in virtually all neighborhoods. Boston's lowest-paid workers are increasingly in the bizarre position of being required to live in a city in which it is too expensive to live.

Something has to give here.

During the mayoral campaign seven years ago, worker residency became a cause celebre. Boston was a different city then, fearful of its future and looking for someone to blame. City workers seemed a good target. Who, after all, doesn't relish the opportunity of beating up on faceless bureaucrats?

Newly elected Mayor Thomas Menino, one of the biggest proponents of residency requirements during the campaign, vowed strict enforcement.

The City Council, which at times seemed to be panting for the blood of those city workers who dared live in the suburbs, went even  further, pushing through a draconian ordinance. Workers were told to move into the city or they would be fired. A Stasi-like enforcement agency, the Residency Compliance Commission, was created. It hired private detectives to follow workers, checking up on where they were sleeping and, sometimes, with whom.

The casualties were everywhere. Thomas Lyons, the universally admired head of Boston's veteran services, was forced out. (He went on to run the New England Shelter for Homeless Veterans on Court Street, working just as hard for Boston's neediest residents as he ever did.)

Michael Sheehan, a blind, wheelchair-bound employee who worked at City Hall's information desk, was fired. He sued the city, claiming discrimination. Last year he won a settlement of nearly half a million dollars.

And for what?

There is an enormous surface appeal to residency rules, which is why many cities have, at various times, tried to implement them.

Yet the rationale for a residency requirement has always been somewhat confused. Some say it makes for better workers. Others view it as a jobs program. But the principal argument, one made by Menino, was that the requirement would save the city from losing its residential base.

In truth, Boston was losing residents back then. Of course, it wasn't residency rules (or the lack of them) that drove people out. It was high crime and poor schools.

Now it's different. People are moving into the city. Again, residency rules have nothing to do with the change. In what truly is one of the biggest public policy successes of the last decade, crime has dropped precipitously. Boston has as a consequence discovered an important truth about human nature: People will live in the city if it's safe. If they fear for their lives, surprise! They leave.

Are resident-workers better workers? Do they care more about their jobs if they live in the city? When it's been looked at in the past, job performance hasn't seemed to correlate to where workers live. Indeed, in geographically diverse Boston, it doesn't make sense. For example, who has more in common with East Boston: next-doorsea or the Boston neighborhood of Hyde Park, a full 15 miles away?

How about residency as a jobs program? Certainly it's a great idea if you're a politician who likes to hand out patronage. Otherwise, you'd be better off focusing on economic growth and job training.

It's strange. Most of us would be offended if an employer such as Gillette suddenly demanded, on pain of termination, that all of its workers be clean-shaven. Yet that is a fairly small request compared to the much more offensive act of an employer telling an employee where to live. And that is the real flaw with residency requirements: They fundamentally violate workers' rights.

One would have thought that the days when employers could dictate to employees how they conducted their lives outside of the workplace were far behind us.

Circumstances have changed. Boston is not dying and as a consequence, members of the City Council are less rabid about residency than they once were. Will it be possible to loosen the requirements? How about permitting workers to live where they want  but granting as additional compensation a housing allowance to those who live within Boston?

One thing is for sure. Last time around, residency advocates rolled over city workers. This time, employees should not let themselves be so easily demonized. This time, if Boston continues to insist on a rigid residency requirement, they should make the city back up its foolish demands with hard cash.

Tom Keane writes regularly for the Boston Herald.