Questions from several justices during arguments suggested the court could be searching for a middle ground in the dispute between United Parcel Service and former driver Peggy Young.
UPS declined to give the woman temporary light-duty work so she could avoid lifting heavy packages after she became pregnant in 2006.
Young was in the courtroom Wednesday to hear the justices talk about employers' responsibilities under the 36-year-old Pregnancy Discrimination Act.
With some of their male colleagues unusually quiet, Justices Ruth Bader Ginsburg and Elena Kagan repeatedly pressed UPS lawyer Caitlin Halligan over the Atlanta-based package delivery company's refusal to find a temporary assignment for Young.
The anti-discrimination law "was supposed to be about removing stereotypes of pregnant women as marginal workers. It was supposed to be about ensuring that they wouldn't be unfairly excluded from the workplace. And what you are saying is that there's a policy that accommodates some workers but puts all pregnant women on one side of the line," Kagan said.
Defending the company's actions, Halligan said UPS did not provide light-duty work to any employees unless they were injured on the job, had a condition that was covered by the Americans With Disabilities Act or lost their federal certificate to drive a commercial vehicle.
Ginsburg challenged Halligan to come up with an example of someone who asked for lighter duty but didn't get it, other than pregnant women.
"Is there an employee who asked for a dispensation because of a medical condition that restricted her ability to lift, to any single employee?" Ginsburg asked.
Halligan replied, "There's not a name provided in the record because one was not elicited by (Young) whose burden it was."
Young's dispute with UPS arose after she gave her supervisor a doctor's note recommending that she not lift packages heavier than 20 pounds. Young said she dealt almost exclusively with overnight letters, but UPS said its drivers must be able to lift packages weighing up to 70 pounds. Young left the company in 2009.
UPS has since changed its policy and says it will voluntarily offer pregnant women light duty starting in January.
Halligan noted that nine states now have laws that require an accommodation for pregnant workers, and she urged the justices to let elected lawmakers make these kinds of policy decisions, rather than federal judges.
"I want to point out that this is an area where the democratic process is working as it should," Halligan said.
The states are: California, Connecticut, Delaware, Illinois, Louisiana, Maryland, Minnesota, New Jersey and West Virginia.
More than 120 congressional Democrats are backing legislation that would change federal law to make explicit the requirement to accommodate pregnant women. Pennsylvania Sen. Bob Casey said the bill is modeled after the landmark Americans With Disabilities Act.
"It would make sure that pregnant workers have the same measure of protection," Casey said before the start of a rally outside the court in support of Young.
The Obama administration and an unusual array of liberal and conservative interest groups are supporting Young, who lives with her 7-year-old daughter, Triniti, in Lorton, Virginia.
In court on Wednesday, Samuel Bagenstos, Young's lawyer, ran into early trouble from Justice Anthony Kennedy.
"You make it sound as if the only condition that was not accommodated was a lifting restriction because of pregnancy," Kennedy said, calling that a "misimpression."
Kennedy asked just a few questions and Chief Justice John Roberts commented just twice during the argument.
Since the justices agreed in July to hear the case, the Equal Employment Opportunity Commission has updated guidance to employers to make clear that they should accommodate people in Young's situation. Yet the U.S. Postal Service, an independent federal agency, maintains the practice that UPS has now abandoned, UPS said in court papers. The Postal Service declined to comment.
Solicitor General Donald Verrilli acknowledged in court Wednesday that the Justice Department has previously defended the Postal Service in similar lawsuits. Verrilli pointed to the recent EEOC change to justify the administration's shift in legal strategy.
The U.S. Chamber of Commerce is among those on UPS' side. The chamber says many of its members do provide additional benefits to pregnant workers, but it says policies at thousands of companies would be upended if the court were to rule for Young. Lower federal courts have rejected her claim.
Kagan said she was putting forth a "middle ground" that would force those courts to re-examine Young's case with a more accepting view of the discrimination claim. UPS and other employers facing similar suits would then be able to argue their policies were legal because they were based on seniority or some other acceptable reason, Kagan said.
It was not clear how many justices might share Kagan's view.
A decision in Young v. UPS, 12-1226, is expected by late June.
Follow Mark Sherman on Twitter at: http://www.twitter.com/shermancourt