When the inauguration parade rolls down Pennsylvania Avenue in front of the White House next week, Lafayette Park will be packed with Ronald Reagan supporters -- all of it, that is, except for the northeast quadrant.

For the first time in Inauguration Day history, that particular part of the park is being reserved for demonstrators, either for or against the new Republican administration, according to the Dec. 24 Federal Register (page 84997). The rest of the park and the entire White House sidewalk side of Pennsylvania Avenue will be held for the exclusive use of the Inaugural Committee.

It's not that the Reagan people want it that way -- it's required by a 1979 court decision that was affirmed last month by the U.S. Court of Appeals for the District of Columbia.

By law, the Department of Interior's National Park Service regulates demonstrations on government-owned property in Washington. Since 1956, a specific statute, the Inaugural Ceremonies Act, has authorized the interior secretary to grant permits to the Inaugural Committee for the use of whatever federal lands it desired within the District of Columbia.

Quite naturally, Inaugural committees have regularly sought exclusive use of Lafayette Park, which is across from the White House, and have regularly received it.

However, at Richard Nixon's second inauguration Jan. 20, 1973, one person was arrested by Washington police when he tried to demonstrate in Lafayette Park.

That arrest was challenged in the courts and in 1979, a U.S. District Court ruled the demonstrator was "entitled to exercise his First Amendment rights in the White House vicinity on Inaugural Days. . . ." In addition, the court required that the Interior Department establish specific Inauguration Day rules for areas in the vicinity of the White House.

The government appealed and, just over a month ago, the Court of Appeals supported the lower court ruling.

The interim rule, published Christmas Eve in the register, gives the Inaugural Committee all of its normally exclusive permit areas around the White House -- except the northeast quadrant of Lafayette Park -- with access reserved to persons holding special passes or tickets.

As of Friday, no individual or group had asked for a permit to demonstrate in the northeast quadrant of the park, although permits for other areas around town have been sought for counterinaugural activities.