Laws differ,but more on a beach-to-beach level rather than by state. Some beaches only allow dogs during off-seasons, which typically occur from October to the discontinuance of April. Some beaches specify that dogs should be kept on leashes no longer than 6 feet. Still others require that dogs may only walk on areas of the beach that are washed by the tall-tide line, and that dogs be kept out of public areas,such as those reserved for camping, bathing and picnicking. For best results, or do some advance research online or by calling public park authorities to find out what restrictions might apply to the beaches you hope to visit with your dog.
Source: thedogdaily.com