Updated

The American Civil Liberties Union is suing the city of Defiance in northwest Ohio, alleging the city's ban on sidewalk messages shouldn't apply to chalk messages and violates free speech rights.

The city prohibits disfiguring sidewalks by painting words, names or ads on them. The issue arose last year when members of an Occupy protest group were threatened with arrest for writing messages in chalk on sidewalks.

The ACLU's Ohio chapter argued in its federal lawsuit Tuesday that the law is unconstitutional and asked a judge to stop its enforcement. The group also argued the law shouldn't apply to chalk because chalk's not permanent.

Toledo law director David Williams said he hadn't seen the complaint. He previously has said the ban has nothing to do with the messages' content.