Riot sponsored tournaments

Hello everybody, A quick question here. I participate a lot in riot sponsored tournaments, and I would like to know, How do we, as players, as participant in the tournament, know if the tournament is actually legit? Example, I was invited to play in this community's tournament who just started doing daily tourneys, and very few people participate. Actually, only 40 players participate, which is the minimum for a riot sponsored tournament. Is there a way to verify if the tournament is legit? thank you.