paris taxi drivers rioting gets *Uber* execs arrested.

I can guarantee that almost none of those drivers paid for a medallion.
The *company* they drive for likely did (and owns the medallion).
But what they're really fighting is the fact that Uber is not required t(and refuse to) set fees according to what French regulators think taxi fees should be. Meaning that Uber drivers don't charge what taxi drivers charge and the taxi drivers, in addition to raking in huge fees (due to this government price setting) also pay out huge costs (because the medallion owner eats most of what the taxi driver makes).
So, *right now*, the taxi drivers are in a bind - they still have these large up-front operating costs, but Uber is cutting into their income by offering a better service (cheaper and/or better *service*) which the taxi drivers *legally* can't do.
The real solution would be for the taxi drivers to quit and drive for Uber (or start their own ride-share programme) - but they'd rather have the status quo. The devil you know and all that.
When facing a competitor with an unregulated business model, no one *ever* has asked that they be de-regulated, only that the competitor be regulated just as hard.