You can search. Many people will tell you you're allowed an x% of tint on the front side windows, etc... but all cars nowadays come with tinted glass so anything that is applied on after is infact considered illegal. If the police are harsh in your area, then I'd have the rear sides and rear windscreen tinted (light smoke) and leave the front sides. It wouldn't look too bad if you left the front sides clear and had the others light smoke. But it would look a bit silly (imho) if you had the rears done in dark smoke (limo) tint.
I have mine all mine tinted (apart from the front windscreen obviously) light smoke and they're fine. To this day I haven't been asked to remove them *touches wood*.
When you do have them done, make sure you get yourself some Clio weatherstrips/seals. If you don't, then the film will become scratched and you'll have to have them re-done again.