A D.C. Superior Court judge ruled yesterday that demonstrators may protest in the Capitol Rotunda if their protest is quiet and nondisruptive.

The ruling, hailed by civil libertarians, was issued by Judge Frank E. Schwelb as he dismissed criminal charges against 11 protesters who refused to leave the Rotunda during an April 14 demonstration against U.S. funding of contra forces opposed to the Nicaraguan government.

Federal and local statutes prohibit demonstrating in the Capitol, but Schwelb said yesterday that those regulations should be interpreted to include only protests that are disruptive and unruly or take place in areas such as committee meeting rooms. More than 100 demonstrators have been arrested this year under those statutes.

"The First Amendment is too precious and fundamental to be circumscribed in this fashion," the judge said in a lengthy explanation from the bench.

His ruling is not binding on other judges and applies only to the 11 defendants arrested during the April 14 demonstration. Nonetheless, prosecutors, defense lawyers and free speech advocates said Schwelb's ruling would encourage more protests at the Capitol.

"We hail the decision," said Arthur Spitzer, legal director of the Washington chapter of the American Civil Liberties Union. "We think that the First Amendment ought to be interpreted to mean that in a place like the Capitol Rotunda, which is a large space open to tourists and anyone who wants to go there, that peaceful expression of views ought to be considered a constitutional right."

Officials at the Capitol, where security has been increased this year, reacted cautiously to the judge's ruling. "The House will seek to assure there is a proper balancing of the rights of any and all minorities to express their view," said Steven Ross, counsel to the House of Representatives, "and also the right of the government and the need of the government . . . to conduct the people's business."

Schwelb's ruling came after defense lawyers asked the judge to grant their motion for acquittal, arguing that the government had failed to prove its case during a week-long trial. The 11 protesters were arrested along with 45 others at the Rotunda and charged with unlawful entry, unruly behavior in a Capitol building, obstructing a passage in a Capitol building and demonstrating in a Capitol building.

Forty-four of the demonstrators earlier pleaded guilty to the unlawful entry charge, including 11 who pleaded guilty before Schwelb at the start of the trial. In addition, the government had dismissed the unruly behavior charges, and the judge dropped the obstruction counts earlier in the trial.

In making his ruling over the strenuous objections of prosecutor Heidi Pasichow, the judge said that although the statute prohibits demonstrations on Capitol grounds, demonstrations should be narrowly construed to mean those protests that cause more problems than those caused by a large group of tourists.

In this case, Schwelb said, testimony showed that the demonstrators were sitting on the floor listening to speakers whom at times they could not even hear. He said he had heard no evidence that would lead him to believe the protesters had threatened anyone's security or interfered with the workings of Congress.

Schwelb warned the jurors, however, that they should not interpret his ruling as giving individuals unrestricted rights to demonstrate. "The court does not want this court's ruling . . . in any way . . . to signify that people with a cause have a right to do anything anyplace," he said.