There's no basis for blocking a web browser that doesn't comply. If Mozilla came out and said "nah", what exactly would the french government do? ban that web browser? demand every website accessed via france check if someone is running a banned web browser? the absurdity would spiral out of control on its own, it seems best to ignore this so that the europeans can take an official L on regulating web content.
I don't know French law, but some options: * Arrest Mozilla officials if they travel to France * Seize or prevent donations made in France * Seize or prevent the Google-search-is-the-default for French portion of queries * Use international venues like WTO to get a judgment enforceable in the US
That’s not what the WTO does.