(Adds city response, paragraphs 9-10)
CHICAGO, Sept 27 (Reuters) - A Cook County judge on Thursday dismissed charges against 92 people arrested last October during two anti-Wall Street Occupy demonstrations in Chicago and said a rarely applied city curfew law violated their constitutional right to free assembly.
Police arrested more than 300 people during the protests for violating a city ordinance when they did not leave a park near Lake Michigan when it closed at 11 p.m. Violation of a city ordinance was the lowest possible misdemeanor charge.
The demonstrations were held in Grant Park, which was the site of large protests against the Vietnam War during the Democratic Party's convention in Chicago in 1968. The area has been a gathering point since 1835, two years before the city was incorporated.
The demonstrators contended the curfew was unconstitutional because it acted as a blanket bar on all speech and was enforced arbitrarily against them. The city said it was applied regardless of speech and the demonstrators had other avenues in which they could communicate.
Cook County Court Judge Thomas Donnelly said the city has made "ad hoc exceptions to the curfew for permitted groups."
"Grant Park's history makes clear: it constitutes the quintessential public forum," Donnelly wrote.
Donnelly noted in a written ruling that the city arrested the demonstrators at the Grant Park Occupy rally, but none of the supporters of President Barack Obama at a victory rally that ran past curfew in the same park in 2008.
"Hopefully this sends a clear message to the city that they must better respect the First Amendment rights of protesters no matter what their message might be," Sarah Gelsomino, a People's Law Office attorney who represented the demonstrators.
Roderick Drew, a spokesman for Chicago's law department, said the city was disappointed with the decision and will appeal.
"The curfew is an important part of the city's efforts to maintain and protect public health and safety, and we cannot allow all city parks to remain open 24 hours a day - nor would other major cities," said Drew, in an emailed statement. "We believe the ordinance is valid and we will therefore continue to enforce it."
Police arrested 173 people at a demonstration on Oct. 16 and another 130 on Oct. 23 for violating the city park curfew. Most had already accepted a deal to perform community service rather than take a conviction. (Reporting by David Bailey; Additional reporting by Mary Wisniewski; Editing by Jackie Frank and Eric Walsh)