OK, that law I would ban.i would ban driving while talking on a cellphone, seriously. Unless you had a hands free device to use it with.
We have that law in CA now, and it's absolutely stupid. By allowing hands-free devices, you are maintaining that the distraction is caused by physically holding the phone, not talking on the phone.
So why is smoking in the car still legal? Or eating? ...All of these activities are exactly the same, in the sense that you are holding something in a hand that should be on the wheel of your car (which is the main problem, right?).
Actually no, it's been proven that talking into hands-free devices is just as distracting (and just as dangerous) as talking into the cellphone handpiece.
Basically, the law is inconsistent and doesn't support any science. You either ban the use of cellphones in automobiles entirely, or not at all (or, if you really want to allow hands-free devices, then you must ban all other activities that take up a hand while driving).