Right now the prevailing attitude is that it's legal and nobody will get prosecuted for it. It's certainly possible for this to change, but premined altcoins (creators mine a % before making it public) and other alleged scams such as Quarkcoin (Max Keiser & Bill Still) have happened repeatedly.

My statement was from the angle that if you get ripped off in a situation like this, there is no recourse for you, and not legal advice that you cannot get in trouble for participating in these activities.