Opponents of Maryland's plan to build twin sports stadiums in downtown Baltimore were elated this month when a judge ruled that the plan could be placed on a statewide referendum in 1988.

They should know soon whether their excitement was premature.

Maryland Attorney General J. Joseph Curran is expected to argue before the Maryland Court of Appeals today that the lower-court ruling should be overturned, and advocates and foes of the stadiums say they expect the court to make a speedy decision.

Anne Arundel Circuit Judge Raymond G. Thieme Jr. rejected the state's contention that the $201 million stadium plan for the Camden Yards site near Baltimore's Inner Harbor should be exempt from referendum because it is an appropriation for maintaining state government.

Opponents of the stadium plan have collected more than 45,000 signatures -- much more than the law requires -- to place the issue on the ballot in November 1988. Gov. William Donald Schaefer says that such a delay, regardless of the outcome, could doom Baltimore's chance of landing a National Football League franchise and harm efforts to keep the Orioles baseball team in the city.

Because of the importance of the issue, the Court of Appeals accepted the case on an expedited basis. Some of the lawyers involved in the case say they believe that there will be an expedited decision. -- Robert Barnes