In theory, someone can sue as long as a lawyer is willing to take on the case or you are willing to go through with the case. Unfortunately, the question is will a court recognize fantasy football monetary claims as valid. Firstly, we must determine whether the league you are a part of is valid.
Under federal law, fantasy leagues are legal as long as they follow the following criteria:
If your league is legal, you've already put yourself in good standing to make sure your perceived winning are received. The first step will be to do research on your league, that is the players responsibility.
Certain state laws crack down on gambilng, "play for cash" games do not violate gambling laws so long as chance is not the determining winning factor. If you can prove that chance was involved, you may have a viable case on your hands. Again, this is to be determined by a lawyer.
Ultimately, you have the ability to take a case to small claims court with respect to fantasy league pools. It is up to the court to determine validity based upon state gambling rules, and whether the league should be in operation in the first place.