I can see the point in outlawing it. Showing your own face, communicating by your eyes and showing that way who you are, is paramount in most parts of the world and it's long been central to the Western world. By showing your face and showing that it's really you speaking you vouch for what you think, what you're going to do, what you stand for as an individual, not just as a grey member of a group. It's a way of communicating "This is sincerely me" - and of making it easy to grasp and verify that this is the same person who signed papers, attended class, did a job, visited hospital etc at some earlier date. If you hide your face, there is always the suspicion that you're being booted around by somebody else, or that there's lying involved. Remember, the law would only apply in public, not at home, and maybe not even to passengers in a private car.
So outlawing the burqa could be a way to show, even if a bit brusquely,. that "nobody outside your little corner will listen to you if you hide your face". The question though is, how far is this going to reach those women, and how will the law be put into action? It's not a huge number of people that wear full-covering veils anyway in Europe -the estimated number in France is less than 3.000 in a country of 65 million people - and those who do often don't speak the language of the country (French, Dutch etc) so they won't really be easy to reach. Again, some women who come as tourists from, like, Saudi Arabia to Paris do wear burqas: would the police yank them in while they're walking down the Champs-Elysées in Paris buying jewellery? Not likely! So the law could become sonmething that only gets enforced in some places and gets used as a tool for making people bend by threats.
There are sound reasons I think, the aim to make these people act like true citizens and to protect their daughters from being pulled into a kind of family control, a suffocating family seclusion that really does happen - those are legitimate concerns. Modern secular school of any kind is pretty much impossible if you're wearing a burqa all the time at school, making a bid for a job becomes useless too. And then there's public safety, that's a reason that just didn't exist twenty years ago: nobody tried during the French-Algerian war or during the Palestinian assaults of the 1970s to enlist women as covert suicide bombers (at least no one was successful in staging such an attack, as far as I know) but that actually happens today. i dont think one can disregard that to many people, a woman in a burqa represents an immediate threat because she might be carrying a bomb or a gun, and that's something she cannot really disprove except by removing the garment, which is just what she doesn't want to do, or even feels forbidden to do.
Sure enough it's a restriction in the right of people to express themselves through what they choose to wear. I still feel the solid reasons in terms of community and citizenship outweigh that. Then making the law work, like I pointed out, is another matter.