A federal judge, hearing the case for the second time, rejected D.C. police arguments and ordered early this morning that the Christian Knights of the Ku Klux Klan be allowed to march today from the Washington Monument to the Capitol along Constitution Avenue.

U.S. District Judge Louis F. Oberdorfer held an emergency hearing last night to determine a route for the march after the U.S. Court of Appeals here overturned his earlier ruling permitting full use of Constitution Avenue.

D.C. police, arguing for a shorter route, have contended that they could not ensure the safety of the marchers over the full route.

But in ruling from the bench early this morning, Oberdorfer noted that the U.S. Park Police, an arm of the federal government, is to join in providing security at the march.

Although there might be a threat of violence beyond the control of the D.C. police alone, the judge said after more than three hours of testimony and argument, "I can't find that the United States won't meet its commitments."

About 50 Klan members are expected to participate in today's march, which is to begin about 1 p.m. at 14th Street and Constitution Avenue NW and proceed to the Capitol for a planned rally.

The city had appealed the judge's original ruling permitting the march from 14th Street to the Capitol, but a District government lawyer said early this morning that it would be difficult to appeal the latest ruling in time.

"We won," Klan leader Virgil Griffin said early this morning from his Mount Holly, N.C., home after being informed of Oberdorfer's latest ruling. "We're fixing to leave right now. Maybe it will go to appeals, but we're coming anyway." The ruling was also hailed by Arthur Spitzer of the American Civil Liberties Union, who argued for the Klan's constitutional right to march over the full route. "We hope the citizens of the District of Columbia will cooperate in maintaining peace in the city and protesting the march in a peaceful way," Spitzer said.

Earlier in the day, when the route was still in doubt, Griffin vowed to march alone if necessary.

"I don't need a permit to walk that street by myself," he said. "I will wear my purple robe and I will make my walk."

Thousands of counter-demonstrators are expected at the march.

The latest legal decision follows an unusual and public argument between D.C. police and the U.S. Park Police over jointly staffing the march route.

An alternate route to the one that covered seven blocks of Constitution Avenue was a seven-block march along nearby Madison Drive on the Mall, which is under Park Police jurisdiction. Griffin asked for that route as an alternative after D.C. police told him that they were reluctant to issue a permit for the 11-block march.

The National Park Service delayed issuing the Klan a permit when it discovered that D.C. police were refusing to assist Park Police on the Mall route, as is routine. Park Police in turn said they could not protect the Klan on Madison Drive and began an appeal to other federal law enforcement agencies for help.

In the split decision yesterday, Appeals Court Judges Harry Edwards and A. Raymond Randolph agreed with the city that a four-block walk along Constitution Avenue is sufficient to guarantee the Klan's right to free speech. Chief Judge Patricia M. Wald disagreed.

Edwards's opinion said that the four-block permit "does not cause irreparable harm" to the Klan. He said the lower court failed to rule on several specific points, including the assumption that permit holders always are allowed to parade the full length of Constitution Avenue, that absent the threat of violence against the Klan, they would have been given the longer route, and that threats of violence never may be considered in assessing a permit application.

Randolph said the Klan could "make its point regardless whether its members march one mile or two. But the Klan's members will not be able to take a single step without police protection."