Well-established law, going back to Roman law, to the Justinian Code in fact, turned out to be weirdly clear on the status of the intertidal. It's crazy to read, like Roman futurology: The things which are naturally everybody's are: air, flowing water, the sea, and the sea-shore. So nobody can be stopped from going on to the sea-shore. The sea-shore extends as far as the highest winter tide. The law of all peoples gives the public a right to use the sea-shore, and the sea itself. Anyone is free to put up a hut there to shelter himself. The right view is that ownership of these shores is vested in no one at all. Their legal position is the same as that of the sea and the land or sand under the sea.