COMMERCE : Unions Seeing Red as German Blue Laws Ease : Much to the chagrin of labor, local governments chip away at the country’s sacred free day with occasional Sunday openings.

Although Lieselotte Jaeckel has worked at the Karstadt department store here for 18 years, Sunday was the first time she ever labored on the traditional day of rest.

For four hours of cashiering, Jaeckel received 2 1/2 times her normal pay, transportation costs and a small bottle of sparkling wine--a token of management’s appreciation.

And yet, “I’ll never do it again,” Jaeckel said. “It’s clear this is the first step toward Sunday work.”

Sundays are feiertag in Germany, free day, rest-and-recuperation day, a time for the family in a hard-fought, union-won, 37 1/2-hour workweek in which stores close at 6:30 p.m. on weekdays and 2 p.m. on Saturdays.

But Kaiserslautern has joined a growing number of German towns chipping away at that tradition via a loophole in the country’s strict law on store hours that prohibits Sunday shopping. The law says a community may open stores up to four times a year in connection with a local fair or festival.

The results are, of course, mixed.

Customers are happy, workers are mad, and the union is suing the city.

Kaiserslautern belongs to the western state of Rhineland-Palatinate, which once had a central administration to which communities could apply to open on special Sundays.

The larger cities in the state had an unwritten agreement never to do so. As long as one stayed closed, the others did not have to worry about losing business to the competition. Thus, stores could avoid overtime and union confrontations.

But authority to decide on Sunday shopping was given over to the communities, and, in the middle of a recession last year, Social Democratic Mayor Gerhard Piontek and the Kaiserslautern retailers group decided to try it. The city of 100,000 has 15% unemployment and loses customers to larger municipalities of Mannheim, Karlsruhe and Mainz.

Big department stores did not join in last year. But when they saw the huge Sunday crowds, they also saw the writing on the wall. This year, they opted to open.

The decision was not easy. About two months ago, Karstadt manager Wolfgang Pohl asked his betriebsrat , or mandatory in-house union council, to agree to the October opening. Workers said no. The store took the issue to arbitration and won the right to open after agreeing to 150% overtime pay--10 hours wages for a four-hour day.

The German retail workers union then sued the city and sought a temporary injunction to block the opening. They lost when an administrative court in Koblenz ruled that working one Sunday a year does not represent undue hardship for clerks; the long-term challenge of the legality of the special Sunday openings is pending.

Hermann Heinrich, Karstadt’s union leader, said that if the workers agree to one Sunday, management will want four, one city will follow another and soon workers will be asked to work nights, weekends and all sorts of unorthodox schedules. “This law is for the protection for workers,” Heinrich said. “There’s a domino effect.”

German workers are among the world’s highest paid and best cared for. They normally get six weeks of vacation a year, a 13th month of salary, plus extra Christmas and vacation bonuses. They fear an expansion of their workweek and, because management is always trying to cut labor costs, believe no new employees would be hired if shopping hours are lengthened.

Union representatives and even many retailers insist that German shoppers stick to a fixed budget, do not buy on credit and do not spend more money when shops are open longer. So why do so? “If you wake up a demand in the customer, he will have this demand in the future,” Heinrich said.

But the demand, it seems, is already there.

“Sunday shopping is great,” said Karin Persau, 33, a working mother who normally juggles shopping on her lunch hour. Pointing to clothes she had bought for her husband and daughter, she added, “I probably wouldn’t have bought these things if I hadn’t gone shopping today.”

And on Monday, Karstadt manager Pohl declared the previous day “a full success,” with sales as brisk as a Saturday before Christmas.