Exxon Mobil could afford to wait for this day. The entire region it damaged couldn't.

That's the ultimate insult to come from last week's Supreme Court ruling that slashed punitive damages over the Exxon Valdez oil spill by roughly 90 percent. The oil giant dragged out the legal process for two decades until it got the slap on the wrist it wanted.

Long ago the courts tagged Exxon Mobil with the blame for the spill, which left 11 million gallons of crude oil oozing through Alaska's Prince William Sound in 1989. This, after all, was a company that entrusted the mammoth of its fleet to a lapsed alcoholic, Joseph Hazelwood, who wasn't even supposed to drive a car.

On the high court's plate this time was a decision whether the company owed any punitive damages to the victims and, if so, how much. After they were initially awarded $5 billion in the early 1990s, the Supreme Court's 5-3 vote reduced that to roughly $500 million.

That still would send about $15,000 to each plaintiff. This money, though, isn't aimed at making things right for victims. It would be impossible to accomplish that; studies show the disruption of animal habitats, upon which the Alaskan economy relies for tourism and commercial fishing, will linger at least several more years.

Instead, punitive damages aim to send a message to the offender to shape up, and it's difficult to see how this decision serves as any kind of deterrent for Exxon Mobil. To a company that rakes in double-digit billions in a single quarter, $500 million is a drop in the ocean. During the marathon court battle, the company accumulated enough in interest earnings alone to wipe out that burden in a month or two.

Most disturbing was the court's vaguely reasoned guideline for future lawsuits. Justice David Souter wrote in the opinion that punitive damages should never be any higher than compensatory damages. Those are the ones that reimburse victims for actual costs they can prove, like the loss of fishing income after an oil leak.

We agree massive fines are too often arbitrarily plucked from the air. Except the artificial ceiling the judges set wasn't rooted in law, either.

For nearly 20 years the residents of Prince William Sound played by the legal rules they were dealt, only to have a majority of the justices make new ones. In his dissent, Justice John Paul Stevens observed astutely that caps on punitive damages "are typically imposed by legislatures, not courts".

If any firm deserves the most forceful smackdown, it's Exxon Mobil. Yes, the company accepted some degree of responsibility in paying out hundreds of millions to those affected by the Valdez spill.

Yet its mistakes were by no means limited to lazy oversight of an employee. The company botched the cleanup effort as well, cutting corners and making half-hearted attempts in the critical early days.

In 1989, the nation was outraged by video images of writhing otters coated in black oil. Little did it know an erroneous court decision 19 years later would close the chapter by leaving a similar black mark on the judicial system.