Boxing was illegal throughout France immediately after World War I (and perhaps during the war as well) - except at the Paris-based National Sporting Club, so long as the bouts were for (and by?) members of the club. Source: January 1919 newspaper microfilm.
December 15, 1918: Boxing is to resume in Baltimore where it had been banned during the war. Source: ditto.
In fact, from my newspaper research, there were countless legislative bills being considered in many US states immediately after the first World War had ended. I've only gotten through January 1919 newspaper microfilm, but this seems to have been the trend. (Along with the campaign to outlaw alcoholic drinks in the US; by January 1919 enough states had ratified the proposed US Constitutional Amendment to make America "dry." And we know by now what happened as a result of that stupid legislation.)