Are you in the UK?
Yes any promo by a casino where there isn't a free to enter route would be governed by the Gambling Act 2005, the difference is, here the casino have specifically said their gaming license wasn't used, so if Nickslots doesn't have his own then it was an illegal lottery, which won't look good for Rizk as they were involved in it.
If you are in the UK then have a look through the Gambling Act and this
from that link
In simple terms a lottery is a kind of gambling that has three essential elements:
payment is required to participate
one or more prizes are awarded
those prizes are awarded by chance
If it is a raffle and you don't require a deposit to be made then it would be unlikely to be classed as a lottery, so if you said, sign up and send you the user name to be entered into a draw, then that would be a prize draw, no payment required and it is a free entry. If you added 'and deposit £10' then payment is required and there is no way to enter for free, then its classed as a lottery and you are bound by the gambling act, assuming you are in the uk
Hope that helps