WASHINGTON -- Several National Day of Prayer observances took place in the nation's capital Thursday, but 2010 could be the last time the event is observed if the White House fails in an appeal against a court ruling that the day violates the ban on government-backed religion.

Wisconsin-based U.S. District Court Judge Barbara Crabb ruled April 15 that the federal law designating a National Day of Prayer and requiring an annual presidential proclamation of the National Day of Prayer violates the establishment clause of the Constitution's First Amendment.

Despite that ruling, several observances took place Thursday, including at the Pentagon, the Cannon House Office Building and on the steps of the U.S. Capitol.

In her decision, Crabb said until the defendants in the case exhaust their right to appeal the decision, observance ceremonies could proceed.

The Freedom From Religion Foundation, an association based in Madison, Wis., that filed the lawsuit against the government, held a rally protesting the day of prayer at the Wisconsin state Capitol.

Charles Haynes, a First Amendment scholar specializing in religious liberty at the Washington-based Freedom Forum, said he expects the president to succeed with his appeal.

He also said Crabb was merely being consistent with past rulings and essentially saying "what everybody knows about the inherent (constitutional) contradiction of the National Day of Prayer."

"The courts are not immune to public dissatisfaction," he said, adding the Court of Appeal could cite a 1983 Supreme Court decision that upheld the right to legislative prayer, on grounds "the offering of prayer is a tolerable acknowledgment of beliefs widely held among the people of this country."

"It is possible the courts would argue that the Day of Prayer goes all the way back to our Founding Fathers, and that they are not going to disturb it," he said.

Also, evangelist Franklin Graham prayed on a sidewalk outside the Pentagon on Thursday after the Army decided two weeks ago to rescind an invitation to its National Day of Prayer service following an objection by the Military Religious Freedom Foundation that Graham previously had insulted people of other religions, particularly Islam.

Graham is the honorary chairman of the private National Day of Prayer Task Force that leads national events where all the prayers are strictly Christian. The Army said its leadership decided that Graham's past comments were "inappropriate as a speaker for an open religious service."