While the spirit of Christmas is not litigable, some of the religious trappings of the holiday season are more and more being subjected to judicial airing.
At issue now is whether publicly sponsored displays of the Nativity scene are in violation of the constitutional guarantee of separation of church and state. The legal questions still need to be refined - but the emotion surrounding the dispute may parallel that expressed over the controversies about school prayer and public aid to parochial institutions.
And since lower courts continue to hand down conflicting decisions on the Nativity question, legal experts predict the issue will likely end up in the US Supreme Court.
The debate over the Nativity scene heated up recently when a Boston-based US Court of Appeals for the First Circuit banned a Pawtucket, R.I., creche on the grounds that it violates the Constitution. It has been a Christmas tradition there for 40 years. The seasonal placement of the city-owned tableau depicting the birth of Jesus was initially challenged by the American Civil Liberties Union in 1981. And a federal court in Providence upheld ACLU's position. Last December, a group headed by Pawtucket's mayor erected the display on private property pending an appeal of this ruling.
The new edict not only settles, at least for now, the dispute for Pawtucket, but it is binding on areas within the court's jurisdiction in Maine, New Hampshire, Massachusetts, Rhode Island, and Puerto Rico. And it has already triggered reverberations elsewhere.
For example, civil rights groups are considering a challenge of Providence's City Hall Nativity scene erected by the Knights of Columbus. And the City Council in Cambridge, Mass., is probing the possible effect of the Pawtucket ruling on its municipally based Nativity scene decorations.
Other communities appear to be in limbo over the issue. Mayor Maurice Arel of Nashua, N.H., says that despite some protests, his city will keep its creche until there is further resolution of the dispute in this New England state or by the US Supreme Court.
Elsewhere in the nation, Gov. William J. Janklow of South Dakota is bucking an ACLU challenge in insisting that the Nativity scene in the State Capitol rotunda is ''constitutional'' and ''harmless.''
The religious display dispute as a ''church and state'' constitutional issue began to surface only within the past five years. Some communities, such as Santa Monica, Calif., have resolved the issue locally. When challenged by atheist Madalyn Murray O'Hair for placing a privately owned religious scene in a public park, the seaside Los Angeles suburb agreed to an atheist display on the same property.
However, a ruling by Federal District Judge David Winder in 1981 upholding the use of a small Nativity scene on the steps of the City-County Building in Denver could well provide a key argument in defense of creches on public property if and when the issue reaches the US Supreme Court. Judge Winder held that traditional Nativity scene figures - the Madonna and child, Joseph, the shepherds, and the Magi and animals - could be viewed as holiday folklore rather than governmental endorsement of religion.
''It is both a religious symbol of the birth of Christ and a sign of the holiday season on a par with Santa and mistletoe,'' the judge said. ''Its meaning derives from the context of its use and from the eye of the beholder.''
The Colorado case is still alive with new arguments scheduled to be heard before the state Supreme Court.
Some legal observers say that backers of such displays are likely to find their strongest legal footing by playing down the ''religious'' significance of the Nativity scene.
On the other hand, Judge Thomas E. Fairchild, in writing the majority opinion in the Pawtucket case, held that ''erection of a creche had a primary effect of advancing religion and therefore was unconstitutional.'' And in an earlier ruling in this case, US District Judge Raymond J. Pettine rejected the contention that Christmas is a secular holiday in which the Nativity scene loses its purely religious meaning.
''Christmas remains a major spiritual feast for most . . . Christians'' which has gained secular significance without losing its religious meaning, said Judge Pettine, who reportedly maintains a creche in his own home each Christmas.
Americans United for Church and State - staunch defenders of the constitutional principle of separation of church and state - applauds the Pawtucket decision. In an editorial in the December issue of Church and State, AU expresses concern over government attempts to equate the religious aspects of Christmas with the secular holiday.
''The Nativity scene and its meaning can best be preserved by leaving the observance of the Christmas celebration to those who hold it dear,'' AU holds. ''Churches or individuals are perfectly free to erect creches on their front lawns or other private property. That way, the religious significance of Christmas can be preserved, and the spirit of goodwill and interfaith harmony - so often lost in such controversies - can be maintained.''