I would imagine the law does not affect one's dress outdoors but when someone comes indoors they want (everyone) to be uncovered. I know in many states you aren't allowed to wear a halloween mask or disguise into a bank to conduct transactions.
Naturally the reason is due to security.
Understandably this may be a sensitive issue if you dress a certain way because of your religion or culture.
However every nation has the right to draft it's own rule of law.
If I were to go to France I would be obligated to follow (their laws) whether I agreed with them or not.
My other option would be never to go there or possibly try and persuade others not to go as well. Depending on how strongly I felt about it I might petition my country to withdraw it's investments and financial dealings with the country....etc
However in the big scheme of things having an uncovered face inside of public buildings is a very small sacrafice to improve security. I'd take that over being frisked or x-rayed any day of the week!
(Sadly 9-11 changed the world forever.)
Personally I miss being able to see a loved one off at their gate in the airport or being at the arrival gate waiting for them to deboard the plane. None the less I've learned to accept the fact that those days are gone forever.
Therefore I drop people off at the curb and when I travel myself I carry travel size 3oz liquids in a sandwich baggie, remove my belt, my shoes, watch, cell phone, have my bags riffled through, walk through x-ray machines and whatever ever else I'm required to do. I don't take it personally because everyone has to go through the same thing and it's all in the name of the greater good. Unfortunately "some our freedoms" have been stripped away in order for us to maintain the bulk of our freedoms.