A federal judge cleared the way for a possible nationwide rail strike yesterday when he dissolved a two-week old injunction against the Brotherhood of Railway, Airline and Steamship Clerks.

BRAC President Fred J. Kroll said in a statement that the action by U.S. District Court Judge Aubrey E. Robinson Jr. had opened up new "avenues of . . . activity which we shall not hestitate to use as the situation warrants." But Kroll said that the union had no immediate plans to set up picket lines, giving the railroads an opportunity to "asses" the situation.

Robinson issued the injunction on Aug 27 at the request of the National Railway Labor Conference which said that the union was contemplating a strike against some or all of its 73 members, including virtually all of the nation's major railroads.

Conference members have been paying $800,000 a day in strike insurance to the Norfolk & Western Railway which has been struck by the railway clerks since July 10.

Kroll, according to a sworn statement filed in the case by Charles I. Hopkins, Jr., president of the railway labor council, said the union was thinking about setting up picket lines against other railroads because the strike insurance fund was enabling the Norfolk and Western to resist a settlement with the union.

Robinson, who held a hearing on the injunction request last Friday, said in an opinion issued yesterday that he lacked jurisdiction to continue the injunction under federal law. At the same time, he ordered the case transferred to the federal court for the Northern District of Illinois where other litigation is pending between the union and the Norfolk and Western.

Lawyers for the railroads immediately requested a stay of Robinson's order and a new injunction so that they could appeal his decision to the United States Court of Appeals. Robinson scheduled a hearing today on the request.