I am in no way defending this decision, just pointing out that using a mobile phone hands-free is currently not an offence in itself.
My views on this are well documented in the WB archives.

There is increasing researched evidence which points to the fact that conversing in conversation requires a greater level of concentration from the human brain than holding an object. Therefore, based on the numerous articles I have read on this subject, I have formed the opinion that whether it is a hand-held or hands-free device being used, engaging in conversation with someone on the other end of a phone is a huge distraction whilst driving.

Perhaps it’s time the current law was revisited by the legislators.