Nothing can be done, unless you stop playing poker or caught by you they do collusion or you really know the characteristics of certain gambling collusion, But I am not sure that it is known that other users as far as I know the activity is one of the hidden agreements and is very confidential between two parties.

I have heard from my friend who held a poker tournament at the dealer and players in taking deceptive actions against other players in card players often done, starting from the action Bribery or manipulating rules for personal gains often occurs, for that honestly I do not like to gambling poker, but the way they do is very confidential, on average it is never known.