If you are going to bring obstruction charges you will want to base them on something greater than license violations. That's akin to the cop threatening me with obstruction charges for warning other motorcyclists about a speed trap. Conspiracy, on the other hand, is a serious crime unto itself.

I'm not sure i agree with your example, but i'm just saying, there was an actual criminal investigation if they wanted to play that game.

(Your example is not close to what happened here, as again, that would have been more okay. They did not warn the drivers. They hid the law violating drivers from the cops when they knew the cops were looking for them, and did so to make themselves money. It would be more akin to being able to change what the cop sees so that, at your command, all he saw was people going the speed limit, and nothing else)

Those were all civil, not criminal.

Errr, the ordinances in question made it a misdemeanor with an X$ fine. Those are criminal, not civil. Example: http://www.local10.com/news/key-west-police-arrest-unlicense...

"Operating without the required licenses is a second-degree misdemeanor. Illegal drivers face a fine of up to $500 and/or 60 days in jail."

I'm not sure why you believe they are civil. They pretty much never are.