Civil disobedience is the refusal to comply with certain laws as a form of protest. Often these are valid laws, such as a prohibition on obstructing ingress or egress to a building. The First Amendment generally does not protect such acts.
When a crowd of protesters is in a place that police believe the crowd cannot lawfully be, the police must carefully distinguish between those protesters who intend to be arrested for civil disobedience, and those protesters who do not know their presence is unlawful. The best police practice is individualized commands to leave on threat of arrest, followed by a realistic opportunity to leave. Thus, during the spontaneous anti-war mass march in Chicago at the start of the Iraq War in 2003, it was unlawful for police to arrest 900 people on Chicago Avenue without first notifying them that they must disperse or be arrested.
An Illinois statute and a Chicago ordinance prohibit resisting arrest. The former has been applied to “going limp” during arrest. The latter specifically prohibits passive resistance to arrest, as well as active resistance. Thus, a person who commits civil disobedience, and then goes limp during arrest, might face charges both for their initial act of civil disobedience, and also for resisting arrest. On the other hand, mere argument with a police officer about the validity of an arrest, without some physical act which impedes the arrest, does not amount to resisting arrest.