"the right of the people peaceably to assemble"
You are correct, but the law in question does not make this distinction. The right to peaceably assemble is being infringed by this law. If an assembly is not peaceable, then there are laws already on the books to deal with such gatherings. Those laws should be enforced, but laws restricting the right to assemble based solely upon the activity of assembling (such as the one being discussed here) are blatantly unconstitutional.