Its a quirky situation (not that I am an expert) but it is illegal to listen to ATC but I have never heard of anyone getting prosecuted, bearing in mind that at many airports there are groups of people with binoculars in one hand and radios in the other, but, it is more frowned upon to broadcast it and within the UK I have never heard of it happening in any widespread way.
There are numerous websites that do broadcast ATC from other parts of the world, if you go onto
Listen to Live Air Traffic Control Communications | LiveATC.net you will find a few