If you went to a casino you were banned from, you committed trespass: the law is very clear that casinos may ban people. Therefore, there is relatively little that a lawyer could likely do for you. At that same time, the penalty for a single instance of trespass is very low: while a lawyer will always give you some advantage (E.g. from their negotiation skill and knowledge of procedure) and if you can afford one, an attorney should be retained, if the cost of a lawyer is an issue for you, you could reasonably represent yourself in this matter. If you do, be respectful, contrite, and promise not to do this again; it is very likely that if trespass was all that happened, that you will get a favorable plea offer.