From WaPo:
Police Fortify Numbers for War Protests
Demonstration Will Be the First Since the District Passed Arrest Law
D.C. police have canceled days off and are planning to deploy several hundred officers during an antiwar demonstration next weekend that will include a march near the White House, but officials said they expect no trouble.
Saturday's rally, part of a weekend of protests and counter-protests, will be the first demonstration allowed to surround the White House in more than a decade. It is the first major rally to occur since a D.C. law that requires police to give clear warnings before arresting demonstrators took effect.
Passed in response to the much-criticized mass arrests of protesters at a downtown park in 2002, the law also restricts the use of police lines to contain nonviolent demonstrators and requires that police wear clearly identifiable badge numbers. Police also may not stop spontaneous rallies -- as long as such incidents do not clog sidewalks or violate traffic laws -- by arresting demonstrators for protesting without a permit.