What should be done in this family situation?

My brother and sister have rented a house on the beach for a week in July. The house is pet-friendly, with the rule stating only one dog. The local law states that any dog outside, specifically on the beach, must be kept on a leash.

My brother plans to bring both of his dogs. He runs every morning, taking the dogs with him, not on a leash. At least one family member is allergic to dogs. He is friends with several people who have cared for the dogs while he is out of town.

I told him my concerns. The responses were: “The dogs are well behaved” (a slight exaggeration). “The leash laws aren’t applicable everywhere” (they are where we are staying; I checked). “The child with the allergy can take medication”.

This is a man with a heart of gold, yet he is blind when it comes to his dogs and believes that any rule, law, or consideration for others is void.

What should be done at this point?