It is not every day the august members of the US Supreme Court don their black robes to contemplate a fish tale. But that’s what happened on Wednesday.

The tale starts like this: Seven years ago, a marine fisheries officer boarded a commercial fishing boat 100 miles west of Tampa in the Gulf of Mexico.

Upon inspection, he discovered that the crew of the Miss Katie had landed 72 red grouper that failed to measure up to the 20-inch minimum size requirement. The officer wrote boat captain John Yates a citation, packed the undersized grouper into a box, and instructed Yates to deliver the box to officials when he returned to port.

Here’s where the story gets interesting. On the way back to shore, Mr. Yates told a crew member to throw the undersized grouper into the sea and replace them in the box with larger fish.

It might have worked, but upon opening the box federal officials smelled something … fishy. They questioned a crew member, who admitted replacing the fish.

What happened next is the reason this fish story found its way to the nation’s highest court.

Rather than simply citing Yates for violating federal size limits, federal prosecutors used a provision of the Sarbanes-Oxley Act, a law passed in the wake of the Enron scandal, to charge him with obstructing justice by destroying potential evidence.

Instead of a fine and short jail sentence, suddenly Yates was looking at spending up to 20 years in federal prison.

The question before the court is whether the Sarbanes-Oxley law applies only to instances of the destruction of business records in the face of a federal investigation or whether it can also be broadly interpreted to apply to a commercial fisherman’s decision to toss undersized fish into the sea.

The Sarbanes-Oxley Act was passed in 2002 to prevent a repeat of what happened shortly before the collapse of Enron. In that case, the corporation’s accounting firm engaged in a massive effort to shred incriminating documents and destroy databases before any federal investigation could begin.

To prevent similar conduct in the future, the Sarbanes-Oxley Act makes it a crime to destroy “any record, document, or tangible object” to impede any matter within the jurisdiction of the US government.

The key question in the Yates case is whether any “tangible object” can include fish.

Yates’s lawyer, Assistant Federal Defender John Badalamenti, told the justices that “tangible object” refers to things like computers, servers, or flash drives on which records could be stored.

The Obama administration disagrees. Assistant Solicitor General Roman Martinez argued that “tangible object” applies more broadly to cover the destruction of any potential evidence that might be useful in proving a violation of federal law.

For example, federal prosecutors in Boston used the same section of the Sarbanes-Oxley Act to charge a friend of the accused Boston Marathon bomber with helping conceal a backpack and thumb drive that agents were seeking in the investigation of the bombing.

Several justices expressed skepticism about the government’s broad application of the law.

Justice Antonin Scalia asked if there was anything Yates could have been charged with calling for a penalty of lower than 20 years.

He noted that the judge in the case ultimately sentenced the captain to 30 days in jail, but he questioned the decision to charge him under the harsh statute.

“What kind of a mad prosecutor would try to send him up for 20 years?” Justice Scalia asked.

Does the Justice Department offer any guidance to prosecutors before they file charges, Mr. Martinez was asked.

“The general guidance is that the prosecutor should charge the offense that is the most severe under the law,” he said.

He said Yates destroyed evidence, engaged in a cover up, and enlisted members of his crew in the plot.

How big were these fish, Chief Justice John Roberts wanted to know.

“You make him sound like a mob boss or something,” he said. The comment drew laughter in the courtroom.

It was not about the size of the fish, Martinez replied, but the underlying conduct obstructing justice. Prosecutors eventually asked the judge to sentence Yates to a two-year prison sentence.

Martinez agreed with several justices that a 20-year sentence “would be too much.”

Chief Justice Roberts said the potential 20-year sentence offered prosecutors “extraordinary leverage” to insist that a defendant plead guilty.

From there the government’s case started down a very slippery slope.

Justice Stephen Breyer wanted to know if he might be subject to a potential 20-year prison term if he refused to reply to a post office survey and instead threw it in the trash.

He noted that the statute applies to destruction of any document in relation to any matter within the discretion of the government.

Martinez told Justice Breyer that the statute requires proof of bad intent.

Breyer provided it. “I hate postmen,” he said.

The justice said the statute as used by federal prosecutors provided a real risk of arbitrary and discriminatory enforcement.

“You are really asking the court to swallow something that is pretty hard to swallow,” Justice Samuel Alito told Martinez.

Justice Alito wanted to know whether a recreational fisherman in a national park who sees a game warden approaching and throws his undersized trout back into the lake would potentially face a 20-year prison term for obstruction of justice.

Breyer returned with still more examples. What if a camper kicks an ember away after building a fire in a no-campfire-zone? Or what if a park visitor picks a flower and then discards it to avoid being detected by park rangers?

The government wasn’t without its supporters. Justice Elena Kagan seemed sympathetic to a broad reading of the statute. And Justice Anthony Kennedy said he was troubled that a narrow reading of the statute might prove problematic.

At one point he commented: “Perhaps Congress should have called this the Sarbanes-Oxley-Grouper Act.”

A decision is expected by next June.

The case is Yates v. US (13-7451).