I don't agree with this though, Rory has stated in the past that levels 10-20 are 'Chunin' Level.
1-10 Genin
10-20 Chunin
20-30 Jonin
30-40 Anbu (Or other elites)
40-50 Kage
Thats how I look at it, so if there are Jonin level Genin in there then good for them, but blocking other players because they can't play as much is a bad move