Believe it or not, it's illegal to cheat in many states. In fact, some adultery laws call for jail time and hefty fines for cheating. More From Dating + Marriage. No matter what you’re looking for, our 10 Best Adultery Dating Sites have what it takes to find you the affair you’ve always wanted. Featured photo source. Some adultery laws differentiate based on the sex of the participants, dating back to about BC, provided drowning as punishment for adultery. Legal separation can mean different things in different states, so it should come as no surprise that the laws regarding dating after legal separation are also somewhat inconsistent. To further complicate matters, the Uniform Code of Military Justice has its own laws regarding adultery among members.