They were doing more than just trading, they were running an exchange. Running an unlicensed exchange is risky business in any country.
It is a good point but if you think about it: bitcoin is "illegal" per se since the country simply doesn't have a definition or regulations for it. And although it's out of law, it's not prohibited? So how can anyone possibly get a license for something so undefined like bitcoin?
I'm sorry for those guys as well. Their arrest doesnt look fair t me(