Sure in the US they are supposed to have "Just cause" but all that boils down to is what the cop feels like. The cop could say "I thought you were texting", "You crossed the yellow line back there", "you didn't turn on your blinker", etc etc etc....in the end you get pulled because the cop "feels like it".

This bullshit is not about SAFETY it never was and never has been, DUI's, seatbelt laws, etc all that shit is just for $$$$$.