There's plenty of DUI arrests where no drugs are present, the driver blows 0.00 on the breathalyzer, and the only "probable cause" for arrest is an officer's subjective "expert" opinion.

https://www.youtube.com/watch?v=gWyzPpYslYc

People have been arrested because the police claimed that a standard dose of Tylenol the night before was driving under the influence of drugs or alcohol. If a police officer wants to take you to jail you're going to jail.