Let's be honest, no one enjoys being pulled over or confronted by law enforcement. It can be an uncomfortable and stressful scenario for civilians and cops alike, and that's why attitude can play such a significant role in the outcome.
For some, attitude can be the difference between a friendly warning, whereas for others, it can mean spending a night in jail. There are those who would argue that the attitude a cop gives you is the attitude they themselves deserve in return. While that's certainly one way to look at it, we strongly insist it's not the best way.
But just for the hell of it, let's say you're confronted by Officer Unfriendly. They're the quintessential stereotype of a rotten cop, and because of this, you decide to flip him the ole bird. What does the law have to say about giving the Blue the one-finger salute?
In short, Idaho answers to the supreme law of the land on this one. And according to the United States Constitution, a citizen's ability to flip-off a cop or even curse them out, is protected by the First Amendment. But just because the First Amendment allows for it, that doesn't mean a cop can't arrest you for it.
Generally speaking, FindLaw says a crazy little thing called "disorderly conduct" offers police officers "broad discretion to decide what is and is not disorderly."
If the manner in which you flip-off Officer Unfriendly suggests or indicates an intent to disrupt the peace or resist arrest, a cop has the authority to arrest you under the umbrella of disorderly conduct.
Bottom line: yes, it's legal to give a cop the finger, but anyone with an ounce of sense or respect for Rule of Law would never do it.