So let the local officials bring a case.

If a police officer pulls me over and finds that I was driving without a license, they aren't going to let me drive away and file a case the next day. They're going to impound my car. Following that same logic, if a jurisdiction requires licenses for commercial taxi drivers, then operating as a taxi without that license will result in your car being impounded. Why do you feel these should be treated differently?

What does this example scenario have to do with the federal government getting involved in taxi regulations?

Nothing. The comment I replied to was explicitly about local officials, not the federal government.

I would be fine with that, but there's no reason that the federal government shouldn't also bring a RICO case for obstruction of justice.

There are plenty of reasons that they shouldn't. You may not agree with the reasons but they exist.

Well, since you haven't stated what the reasons are, you aren't doing a very good job of convincing me that they exist.

One possible outcome of an FBI investigation is information being shared with local prosecutors on which they might being a case.