This is a dark time for constitutional liberty, but the fate of Saturday's peace demonstration in New York deserves a footnote in tomorrow's history books. The demonstrators proposed a march past the United Nations to Central Park to support the role of the UN inspectors in Iraq and to denounce the prospect of unilateral warfare. But Mayor Michael Bloomberg, citing security concerns, said no.

The most the mayor would allow was a rally at the plaza in front of the UN for 10,000 participants. The overflow was herded into "pens" that the police constructed for miles down the center of First Avenue. Once a demonstrator entered his assigned pen, he wasn't allowed to fraternize with people in other pens. While others marched with dignity throughout the world, hundreds of thousands of New Yorkers were kept behind barricades.

This policy was nothing new. The Bloomberg administration has banned all protest marches in Manhattan since September 2002. Nevertheless, the federal courts upheld the city, enabling it to maintain its hardline position.

For all his sound and fury during eight years in office, former Mayor Rudolph Giuliani never imposed such a sweeping prohibition. Suddenly, the only people who can march are innocuous folk, engaged in ethnic celebration.  The city has granted a permit for 120,000 marchers to strut their stuff at the St. Patrick's Day parade. Only the UN protesters and their ilk are left to freeze in their pens.

As someone who made his fortune creating a media company, Bloomberg certainly knows that the First Amendment doesn't protect only marchers on St. Patrick's Day. The Constitution is especially concerned with the threat of political suppression. During the 1960s, federal judges were tireless in striking down the countless pretexts used by Southern cities to suppress civil rights marches against segregation.

But the federal courts failed to rise to the occasion this time around. When the march organizers went to court, federal judges rubber-stamped the pretexts advanced by the Bloomberg administration. The city emphasized that the St. Patrick's Day organizers work with the police in advance to assure against security risks. In contrast, the peace organizers could not say for sure how large their parade would be. Given this uncertainty, the courts upheld the city's decision to ban the march as a reasonable safeguard against violence.

Of course, political protesters never can control the timing of national crises - and yet their right to march has been a central part of the First Amendment tradition. The city offered no evidence of any clear and present danger to public safety, and the Saturday demonstration occurred without significant incident. If the bare risk of disorder suffices for suppression, we have come to the end of the road.

Hoping to narrow the sweeping force of her opinion last week, U.S. District Court Judge Barbara Jones pointed to the fact that "the nation and the city are currently at the second highest security alert." This makes the decision worse, not better. We are only at the beginning of an endless war against terrorism. Are fundamental political rights to be contingent on FBI decisions to change the alert from yellow to orange? Such a power can be blatantly abused for partisan ends. Nevertheless, the court of appeals affirmed Jones' decision, and time ran out before the full U.S. Supreme Court could give serious consideration to the matter.  So the marchers were kept in their pens, creating a precedent that will haunt us in the future.

This is not the first time the lower courts have crumpled in the defense of civil liberties after Sept. 11. Most notoriously, they have upheld the president's power to detain U.S. citizens indefinitely without trial by declaring them "enemy combatants." As these precedents mount, it is time for all of us to reconsider the grim constitutional order we are so hastily creating.

Perhaps it is a good thing that the Supreme Court hasn't allowed itself to enter the fray too quickly. A pause will allow it to appreciate the high stakes involved. But in the meantime, events in New York should caution us about the frightening ease with which our most precious liberties can disappear.

Bruce Ackerman, professor of law and political science at Yale, is author of "We the People."

Copyright © 2003, Newsday, Inc.

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