It's perfectly possible to have arrangements whereby people's facial features are visible on demand, without resorting to a law which would of course have to include all face coverings anywhere.
For example, it would be technically illegal to go for a run in cold weather in a balaclava, walk down the high street with your motor cycle helmet on, dress up as a giant panda etc etc
Half the runners in the London Marathon would have to be arrested :-)
The law in France is properly unenforceable. It also includes lots of other types of garments also including body suits, now unintentionally (and by that token culturally and religiously discriminatory)
We're in the realms of Monty Python here, not to mention Charlie Hebdo.
Yet oddly it hasn't caused as much protest as it might have done, probably partly because there weren't all that many burka wearers to start with and also because undoubtedly a blind eye (so to speak) is turned to the non-burka offenders (and by that token culturally and religiously discriminatory)