Correction Appended

DETROIT, June 3— For the next three days, anyone wearing a mask in this city or carrying gasoline in a portable container will go to jail. And those in possession of just about anything that could cause a disruption can expect intense police scrutiny.

This is Mayor Dennis Archer's response to human rights campaigners who plan, starting on Sunday, to unleash the same kind of protests that left Seattle with $2.5 million in damage last December after a meeting of the World Trade Organization. In that protest, demonstrators, some wearing gas masks, hurled Molotov cocktails, rocks and excrement at delegates and police officers.

The protests planned here are directed at a three-day summit being held across the Detroit River in downtown Windsor, Ontario. Delegates from the Organization of American States, a coalition of 34 nations, are gathering to discuss ways to bolster trade in North and South America. Mayor Archer hopes his new emergency ordinances will dissuade protesters from even showing up. Meanwhile, the police in Canada are bracing for thousands of demonstrators.

Both Detroit and Windsor, which are connected by the Ambassador Bridge and the underwater Detroit-Windsor Tunnel, are on edge because they share North America's busiest border, with 12,000 vehicles crossing every day. But customs and border officials on both sides said they had no plans to close either entry point.

''We saw what happened in Seattle,'' said Greg Bowens, a spokesman for Mayor Archer. ''In Seattle, the police were caught off guard. We don't intend for that to happen here.''

Groups that plan to protest say the authorities are overreacting.

''We're retirees, we're union members, we're students,'' said Brent Patterson, an organizer for the Council of Canadians, a public interest group. ''We're not a bunch of anarchists bent on throwing rocks and breaking windows.''

Mr. Patterson said many of the three busloads of protesters he has signed up for the trip to Windsor from Toronto were afraid. How can the police ''expect a positive, nonviolent protest when they're creating a climate of fear?'' he asked.

A Web site, Stop the O.A.S., says that ''thousands of people will gather in Detroit/Windsor to nonviolently reclaim the streets and creatively block access to the meeting.''

There are signs that the demonstrations will be comparatively small. In Detroit, a labor union stronghold, protest groups have failed to win the support of any major union.

Still, an international contingent of law enforcement agencies -- the Detroit police, Federal Bureau of Investigation, the United States Border Patrol, the Windsor police, the Ontario Provincial Police and the Royal Canadian Mounted Police -- spent much of this week planning strategy. Mr. Bowens said the Detroit police had conducted riot training and put 4,000 officers on call.

On Friday, while police officers in Detroit were trying to quietly step up their presence at the border, visitors to the other side were greeted by a formidable police presence. As drivers left the tunnel, they were met by Ontario Provincial officers, who stood like sentries at each lane.

And the officers' presence was no less obvious around Windsor's usually tranquil downtown. Officers stood on virtually every corner. And they walked some streets six deep, in sunglasses and bulletproof vests. Mayor Mike Hurst of Windsor vowed to have more than 1,700 officers out.

''It feels so scary to see so many,'' said Yergalem Hagos of Windsor, as she watched Canadian officers walk by her family's restaurant. ''You don't know if it is better to stay open or to be safe and shut down.'' A few shops nearby have nailed plywood to their windows.

Mr. Hurst said the lessons of Seattle had forced officials to be cautious. ''We don't have the luxury of a crystal ball,'' he said. ''No one knows what will happen here or in Detroit. What I do know is that they have a right to come here and peacefully protest and I have the right to make sure we're prepared for anything.''

Photo: Workers boarded up windows in downtown Detroit last week as the city prepared for protests of a meeting on increasing trade in the Americas. (Associated Press)