A U.S. District Court judge in Los Angeles has extended his earlier order barring longshoremen from disrupting traffic at West Coast ports and at an intermodal railyard here.

The International Longshoremen's and Warehousemen's Union is upset over the loss of more than 300 jobs at the Intermodal Container Transfer Facility in Los Angeles. Two weeks ago, Southern Pacific Transportation Co. took over direct operation of the yard and replaced ILWU workers with those represented by a rail union.On Feb. 14, Judge Robert M. Takasugi issued a temporary restraining order against a one-day work stoppage planned by the ILWU for Feb. 17. The National Labor Relations Board in Los Angeles sought the restraining order, arguing that the union's planned job action was a secondary boycott, as the union's gripe was with Southern Pacific and not the shipping lines.

Although longshoremen obeyed the letter of the law and did not picket marine terminals, they did not show up to work at most container terminals, idling about a dozen containerships at West Coast ports.

In his original order, Mr. Takasugi gave the ILWU until last Monday to show cause why his original order should not be extended to a temporary injunction. The union pleaded its case Monday, but Mr. Takasugi issued the injunction prohibiting the union from "threatening or coercing or restraining" shipping lines from conducting business at West Coast ports or from doing business with Southern Pacific.

James McDermott, regional attorney for the National Labor Relations Board in Los Angeles, said the normal procedure now, barring a settlement, will be for the union to proceed with litigation before an NLRB administrative law judge in Los Angeles. Any appeal from there would go to the NLRB in Washington.

Both the Pacific Maritime Association and Southern Pacific report it has been business as usual since the longshoremen returned to work on Feb. 18.