The ocean itself draws the proverbial line in the sand, leaving a debris line of sodden sticks, coral chunks, shells and bits of plastic each time it washes up onto the shore.

In Hawaii, that line is especially important, marking the boundary between public and private, and signifying the point where building setbacks officially begin.

It’s a line that varies naturally from year to year, depending on the size of the swells, the fierceness of the storms.

And it’s a line that has been manipulated by coastal landowners who want to build closer to the ocean than they’d normally be allowed.

To hinder the wave wash, or obscure its evidence altogether, they’ve planted thickets of dense vegetation on some of the most beautiful beaches in Hawaii.

For more than a decade, a handful of Kauai residents have pushed back, winning two key lawsuits that lay the legal framework for halting the ongoing privatization of our public beach. The Hawaii Supreme Court issued the most recent ruling just last month, and it builds on shoreline decisions dating back to 1968.

In its earliest decisions — Ashford and Sotomura — the high court found that state policy intends to give the public as much use and ownership of the shoreline as is reasonably possible. In Diamond I — the decision rendered in the first Kauai case — the justices specifically defined the public beach as extending to the upper reaches of the highest seasonal wash of the waves. That 2009 ruling stopped the state from setting the shoreline at the lowest vegetation line, a practice that typically shortchanged the public.

In response, the state Board of Land and Natural Resources (BLNR) adopted a "multi-variable approach" in which the state surveyor considered various factors, but primarily relied upon a "single-year snapshot" — what he saw the day of the site visit. But that "snapshot" was often blurred by vegetation that had been intentionally cultivated. Kauai residents, alarmed that the state was setting shorelines too far makai, presented photographs showing waves had washed 15 to 30 feet higher before the landscaping was installed.

But the state refused to consider that evidence, and Kauai residents filed their second suit. As the case moved through the courts — a four-year process — the BLNR continued to approve shorelines that favored landowners at the expense of the public beach. The impacts of this policy have been felt throughout the state, and most especially on North Shore Kauai, where many houses have been built dangerously close to the water and one was constructed atop iwi kupuna.

In its Jan. 27, 2014, Diamond II decision, the high court reiterated the findings in Ashford, Sotomura and Diamond I. The justices found that "artificially induced and enhanced vegetation is incorrectly being used to currently locate the shoreline," and directed the BLNR to stop relying on even salt-tolerant plants to set shorelines. They also ruled the state must consider historical evidence, including documentation compiled by non-expert witnesses, like the Kauai folks who brought suit.

Most important, the justices reminded BLNR that it does not have the authority to come up with its own definition of shoreline. That definition, the justices wrote, has already been articulated by public policy and law, and it favors the citizens who have used and relied upon Hawaii beaches for centuries.

When it comes to the shoreline, the ocean and the Hawaii Supreme Court have clearly drawn a line in the sand. Will the BLNR continue to cross it, or finally start to toe it?