Atwater v. City of Lago Vista affirmed that police may make a warrantless arrest for misdemeanor offenses. In the Atwater case it was for failure to wear a seat belt. Additionally, that Supreme Court case affirmed that officers have the Constitutional authority to make a suspicionless search of any person incident to such an arrest.  Vehicle searches in such cases are limited in some respects by another case, Arizona v. Gant.  Regardless of Gant, particles in plain view generally have no expectations of privacy. Be assured this is in the U.S. of A and it pertains to you.