I imagine that there must be some legal definition of what land constitutes the beach, perhaps a distance above the high tide point. In this case, besides the loungers, the hotel also had some permanent structures on the upper reaches of the beach.
I don’t know about Hawaii, but here in California the legal definition is any land seaward of the mean high-tide line. Development regulations typically also prohibit any kind of development seaward of naturally occurring dunes. Dunes usually indicate the mean high-water level in typical storms, so development seaward of dunes, even on private property, is typically prohibited to prevent structures from being destroyed (it’s no different than a municipality prohibiting construction on an unstable hillside). Since construction includes fencing, these laws have the practical effect of providing open beach up to the first dune. Technically people walking above the mean high tide line are trespassing on private property, but with no legal way to post or fence the land, it’s unenforceable. The most a property owner can do is ask the people to leave, and call the police to have them ejected if they refuse.