When Gov. John Waihee appointed her, she had been a trial judge for less than a year. Before that she was a partner at a Honolulu law firm and before that she was a prosecutor. Bedecked in lei and surrounded by friends, family and colleagues, Judge Paula Nakayama was sworn in as an associate justice to the Hawaii Supreme Court on April 22, 1993.

Now, nearly 30 years to the day, she is retiring.

She leaves behind a massive body of work in the form of judicial opinions. Thirty years on the bench have allowed Nakayama to write hundreds of opinions reflecting her views on nearly every area of the law ranging from criminal law to contract law.

That said, attempting to distill a justice’s views on the law from an opinion is always a daunting and risky task. The kinds of legal questions before the Hawaii Supreme Court tend to be very narrow and arise from the facts of a particular case.

There is often very little room for philosophizing. On top of that, a judicial opinion is that of the court; it is what the majority of the justices — and for our supreme court that could be anywhere from three to five — believe the law to be.

But Nakayama has written one of those opinions that comes along and changes everything. The structure, meaning and questions that arise from a single opinion can reshape the law itself and dramatically alter the way our government operates. It can even set lofty goals helping us change the way we govern ourselves.

I think she has written one of the court’s most significant and important decisions of this century.

The Waiahole Ditch system is a series of waterways that was originally built and designed to irrigate sugar cane fields in the early 20th century. After the sugar industry phased out on Oahu, the Commission on Water Resource Management, the state agency responsible for governing water, required all existing users to submit applications for their continued use.

The list of applicants and the parties in this case are familiar to any student of Hawaii’s history. The Bishop Estate, the Robinson Estate, Castle and Cooke, the Campbell Estate and the U.S. Navy were among the parties. Environmental groups, farmers and other stakeholders also intervened.

The administrative hearing to determine who gets what and for what purpose took 52 days and four evening sessions and nearly a year to complete. It would take another 10 months for the commission to issue its written decision.

As it played out in the public, the hearing marked a transition from the old economy and politics of the past with a government and economic structure prioritizing the needs of the sugar industry to an uncertain future where the military, Native Hawaiian practitioners and farmers vied for a share of Oahu’s water resources.

Of course, when the commission issued its decision, it was appealed it and made its way to the Hawaii Supreme Court. The unassumingly titled “In the Matter of Water Use Permit Applications” that came out in the summer of 2000 was nothing short of a landmark.

In the 177-page opinion, Justice Nakayama wrote for the four-justice majority to expound upon the public trust doctrine — a legal concept stemming from the late 19th century that says the government holds public lands and resources for the public’s use and benefit.

Building on cases established early on after statehood when William S. Richardson was chief justice and examining aspirational provisions in the Hawaii Constitution following the 1978 constitutional convention, the court turned the public trust doctrine into “a fundamental principle of constitutional law in Hawaii.” This means that the Hawaii Constitution directs the state to hold natural resources like land, air and water, in trust for the people’s present and future benefit.

Not only that, but the court departed from the old view that tended to value private enterprise over obligations to the public.

“To the contrary, if the public trust is to retain any meaning and effect, it must recognize enduring public rights in trust resources separate from, and superior to, the prevailing private interests in the resources at any given time.”

Justice Nakayama wrote that the constitutionally mandated public trust obligates the state to “preserve the rights of present and future generations in the waters of this state.”

That includes drinking water. It cannot grant or take action that would undermine this trust and it empowers the state to revisit prior diversions in the past.

And in Hawaii, another purpose of the public trust is to “uphold the exercise of Native Hawaiian and traditional and customary rights.”

In summing up her magisterial decision, Nakayama quoted the commission’s projection that “by the year 2020, water demand for projected growth of Oahu will exceed the remaining ground-water resources on the island.”

She added that this “underscores the urgent need for planning and preparation” and commented that “much more work lies in the critical years ahead” for the state “to realize its constitutionally and statutorily mandated purpose.”

The court sent the case back to the commission to reexamine the case in light of these newly recognized constitutional duties.

The decision elevated the public trust doctrine from a 19th century legal concept about land use to a constitutional mandate imposed on the state to ensure that we have enough viable resources for the future. It means that the state holds resources like our drinking water not only for our benefit but for the benefit of Hawaii’s later generations. The case itself has become a key source for the state’s authority and obligation to do a better job at considering the use of natural resources.

The decision elevated the public trust doctrine from a 19th century legal concept about land use to a constitutional mandate imposed on the state to ensure that we have enough viable resources for the future.

The Waiahole Ditch case is still good law. In 2012, Nakayama wrote for the court about a similar challenge to use permits of waters about the four major streams of the West Maui Mountains. That lawsuit ultimately resulted in a settlement and streams that had been bone dry for most of my life on Maui flowed with water.

The case itself isn’t just about water either. Nakayama wrote that the “public trust, by its very nature, does not remain fixed for all time, but must conform to changing needs and circumstances.”

Indeed, her opinion has set the tone for some of the major environmental and administrative law cases we have seen this century.

Justice Nakayama’s opinion continues to raise intriguing questions for the future. We will face rising sea levels, longer droughts, and ferocious storms caused by climate change. What does that mean for the public trust doctrine? And what about the state’s obligations when it comes to how close the leaking jet fuel in Red Hill has come to Oahu’s drinking water?

What about those resources we can’t see? Does our government have a duty under the public trust to ensure that people live in places with ample windows with natural light and access to fresh air?

As we face the challenges of living on an island with finite natural resources, aggressive building projects and a changing climate, the public trust doctrine will help us define what it means to live in Hawaii.

We will continue to look to Justice Nakayama’s landmark opinion that has set her place in our state’s legal history.