Hmm. But local taxi regulations are not federal law, so what's the underlying federal crime being committed?

I'm not a lawyer, so I don't know. It just seems to me that if you use infrastructure that crosses state borders, e.g. a telephone or a computer network, to facilitate a crime committed in a state the Federal government has at least some reason to bring a criminal case. I suspect it'd be a law passed under the Interstate Commerce clause of the Constitution.

If money is moving from one state to another, then I would assume it's considered Interstate commerce, which is federal jurisdiction.

Sure, but what federal law was broken? I wasn't aware that the federal government enforces local city regulations just because money is moving between states.

I mean, if the feds really wanted to get in to it, Uber is probably guilty of money laundering.

Their service was illegal under local law, Uber moved the money from their illegal activity in to the banking system and across state lines and a slew of other things that would likely trigger the very broad money laundering laws. Interstate transfer of proceeds from a criminal activity is almost certainly an activity the feds can look into.

I'm guessing the feds can also "assist" the local jurisdictions in the case that the local criminals are an interstate organization that has been committing a slew of crimes across the nation.

RICO explicitly defines racketeering to include several kinds of state law violations

Electronic surveillance techniques could be one angle.

Good ol' wire fraud!