Legal Question in Traffic Law in California

No and No. They need at least reasonable suspicion.

Reasonable suspicion is a legal standard of proof in United States law that is less than probable cause, the legal standard for arrests and warrants, but more than an "inchoate and unparticularized suspicion or 'hunch' ";[1] it must be based on "specific and articulable facts", "taken together with rational inferences from those facts".[2] Police may briefly detain a person if they have reasonable suspicion that the person has been, is, or is about to be engaged in criminal activity; such a detention is known as a Terry stop. If police additionally have reasonable suspicion that a person so detained may be armed, they may "frisk" the person for weapons, but not for contraband like drugs. Reasonable suspicion is evaluated using the "reasonable person" or "reasonable officer" standard,[3] in which said person in the same circumstances could reasonably believe a person has been, is, or is about to be engaged in criminal activity; it depends upon the totality of circumstances, and can result from a combination of particular facts, even if each is individually innocuous.