Illegal to tell someone that they are speaking to undercover cops?

[TriPolar]

@SanVito

Flashing your lights to warn other drivers of speed cameras in the UK is against the law - it’s also illegal to flash your lights for any other reason than warning other drivers that you are there, so we’re not supposed to flash our lights, for example, to let another car have right of way. Our highway code is strict! Of course, we all still do it.

You can’t flash your lights to tell another driver that his lights aren’t on?

[SanVito]

From the horse’s mouth (aka The HighWay Code).

Flashing headlights. Only flash your headlights to let other road users know that you are there. Do not flash your headlights to convey any other message or intimidate other road users.

[Loach]

@ZosterSandstorm

@What_Exit

It has been illegal to interfere with Police Operations for a long time.

I could not find any crime in the California code called “interfering with police operations.” Nor did a search for the words “interfering” or “obstruction” turn up anything that seems remotely close to a blanket law against making a policeman’s job harder.

I think what you mean is that police have considered themselves above the law for a long time, and will arrest people for things that are not crimes if they feel annoyed enough.

I’m not an expert in California laws specifically and will not become an expert any time soon but it appears to fall under PC 148. In my state and in every state I’m aware of it is illegal to Obstruct the Administration of Law. What that entails is contained within the statute and case law and not arresting people because they are annoyed.