They could collect the fine when the blogger enters france or maybe, depending on the case, the european union or an associated state.
But it wasn't "committed in France". This is getting ridiculous, not to mention extremely dangerous. A few more cases of these from the "democracies" of the world, and soon China will start demanding the same thing.
"You said something bad about China online? We're just going to fine you, or ask for your extradition and arrest."
Sure, that can happen. China can and might ask for extradition. This is however a different question from whether the USA will extradite. Extradition is usually denied in cases where the action in question was not a crime in the country that you're asking to extradite.
Think about it: A German commits a murder in the USA which is discovered only after he returns to Germany. Does your "no jurisdiction" line of reasoning still apply?
Did you miss the part where it was an American blogger? It wasn't committed in france.
(BTW, a civil judgment is not "a crime by French law.")
It is not so much about free speech: the two guys have been fined for publishing incorrect information about the financial situation of a bank. It is more about financial regulation than free speech. I'm not so familiar with american law, but I'm pretty sure you got related situations (for example concerning the handling of sensitive financial information, or insider trading, etc.)
Disregarding the question of the reality of what they've been accused of, the fine against Mish is illegal considering the right of defendants to translation and an interpretor has not been respected. This decision will be very probably striken down by any real judge that get her hands on this case.
We have laws that apply to stakeholders and insiders. As far as I know third parties are free to say or even make up anything they want, as long as it's not fraud or libel.
These two things are totally unrelated and I never said the lather would happen.
E.g. I'm Norwegian - Norway claims jurisdiction for certain types of crimes worldwide for Norwegian citizens (quite a few other countries do too).
Enforcability is entirely separate from jurisdiction.
Was this actually a crime or just a civil dispute?
In this case, the fine was pronounced by an independent administrative authority in charge of the regulation of financial markets. No judge was involved in the sentencing.