Terry v. Ohio is the reference here. Unless there is articulable suspicion that a crime is afoot, the detention is, by definition, illegal. Driving while brown (or existing while brown) does not qualify as articulable suspicion of a crime. Therefore, this is an illegal detention - otherwise known as kidnapping. Defending yourself against kidnapping is an understandable position one might take. It might be unwise however, given the criminal justice system is overwhelmingly stacked in favor of law enforcement. That is a personal choice we are free to make so long as we understand the likely consequences of our actions.