Citing “very serious constitutional issues,” a federal judge ruled Wednesday that a reporter for The New Orleans Advocate does not have to reveal unnamed sources he used in writing a 2012 newspaper article that correctly predicted federal authorities were preparing to charge alleged New Orleans drug lord Telly Hankton and several of his associates in a massive racketeering case.

The reporter, John Simerman, was compelled to testify in an unusual court proceeding after U.S. District Judge Martin Feldman allowed defense attorneys to subpoena Simerman and Gordon Russell, another New Orleans Advocate journalist, to testify about a meeting they had with FBI agents just days before the article appeared on the front page of The Times-Picayune. Simerman and Russell both worked for that newspaper at the time.

The hearing raised concerns in media circles because of its potential implications for the free press and the possibility of sanctions should the reporters have refused to identify anonymous law enforcement sources cited throughout the article. But in front of a full courtroom gallery, Feldman made clear early in the hearing that defense attorneys would be strictly limited to asking about a 35-minute meeting the reporters had at the FBI’s Lakefront office and their conversation with Special Agents Richard “Chip” Hardgrave and Keith B. Burriss.

The agents have said they met with the reporters under extenuating circumstances and out of concern that the article could imperil the team of officers preparing to make a series of arrests. Hankton, already a convicted murderer, is one of the most notorious criminals in the city’s recent history, and his operation has been blamed for several retaliatory killings.

Defense attorneys, however, accused the authorities of leaking details to the press about a yearslong probe in an effort to inflame public opinion against Hankton and to prejudice the grand jury considering the case — an accusation that echoes similar defense challenges pursued in the wake of the online commenting scandal that has roiled the U.S. Attorney’s Office.

The defense attorneys argue the indictment, which includes charges of drug dealing and murder, should be dismissed, in large part because a copy of the lengthy Hankton article surfaced in the grand jury room before the panel had returned its indictment.

Arthur “Buddy” Lemann III, an attorney for Hankton, repeatedly asked Simerman to name his law enforcement sources, but Feldman sustained objections by Simerman’s attorney, Lori Mince, citing First Amendment protections. The judge said the purpose of Wednesday’s hearing was to decide whether the FBI agents violated rules on grand jury secrecy — outlined in the rules of federal criminal procedure — and therefore should face sanctions. Feldman said those sanctions could possibly take the form of a fine.

Given the level of detail in the story, Lemann said it was clear a federal law enforcement official — or someone intimately familiar with the grand jury proceedings — had been a source of information for it. Feldman, however, said the story “could equally be information gained by good investigative reporting and good shoe leather.”

“The argument that this court has the right to invade the constitutional protections of the press is ridiculous,” the judge said.

As it became clear the reporters would not be faced with either revealing their sources or being held in contempt of court, the hearing’s focus shifted to the FBI agents and whether their revelations to the reporters amounted to misconduct. During nearly two hours of questioning, Simerman, a veteran journalist who carried a reporter’s notebook even during his court appearance, said his article relied on months of reporting, “dozens and dozens” of sources and had been largely “ready to publish” before he and Russell met with the agents in October 2012.

Russell, who testified only briefly before Feldman adjourned court for the day, had telephoned Hardgrave a few days before the story ran because he wanted the FBI to review and ensure the accuracy of a graphic that illustrated Hankton’s alleged criminal operation, said to involve a hit man and several of his family members. After the meeting, the reporters made some minor changes to the graphic, including removing a photograph of one defendant, Gerard Howard, that Burriss said he did not recognize. Simerman testified that the FBI had “caught our mistake.”

They also removed a photograph of a rapper who ended up not being charged in the federal indictment. Burriss, who has been investigating the Hankton case since 2006, said he asked the reporters why a photograph of Bryan “Baby” Williams had been included in the graphic because he hoped he might gain new insight into Williams’ possible involvement in illegal activities. Defense attorneys, however, claimed that question prompted the reporters to amend the graphic. “We have the FBI making editorial changes to newspaper charts,” Lemann complained.

While the meeting with the reporters had been approved by their supervisor, Burriss and Hardgrave both expressed regret about some comments they made during it. Hardgrave acknowledged he was the “law enforcement source” in Simerman’s article who likened Hankton to “Keyser Soze, the mythically ruthless villain from the 1995 film ‘Usual Suspects.’ ”

“I shouldn’t have done it,” Hardgrave said, adding it was also an “oversight” not to alert the FBI’s media relations officer about Russell’s earlier inquiry.

Burriss also said some of his remarks during the meeting went too far. He said he left the meeting feeling he had given the reporters hardly anything but realized that wasn’t the case when he sat down to draft an affidavit recounting their conversation. “I said too much,” he said, referring to his cautioning Simerman not to print an exaggerated claim that Hankton’s alleged hit man charged $50,000 per hit.

But the agents denied revealing any substantive details about their investigation or the secret grand jury proceedings, and they said they came away from the meeting confident that “no one close to the investigation” had leaked information to the reporters, in part because the newspaper’s graphic left out five defendants who would be charged in the sweeping indictment.

The grand jury had been meeting for a year by that point, had heard from dozens of witnesses and knew “10 times more information than was in the article,” Burriss said.

Assistant U.S. Attorney Elizabeth Privitera sought to underscore the amount of information contained in the article that was available in the public record, for example, details that could have been culled from police reports and previous court proceedings.

Feldman had a number of humorous exchanges with Lemann, teasing him about his bow tie and long-winded questions, but he also appeared to lose his patience at times, saying he would no longer tolerate the attorney’s attempts at theater. “This proceeding could go on until the next presidential election cycle at the rate we’re going at,” Feldman barked at one point.

Indeed, while the judge had hoped to conclude the hearing Wednesday, testimony went well into the afternoon and the judge asked the parties to return at 11 a.m. Thursday. Russell will resume testifying when the hearing continues, to be followed by Todd Cox, a former FBI supervisor, then arguments from the attorneys. Feldman suggested Wednesday that he intends to rule sometime this week on whether to dismiss the indictment or sanction the agents.

Follow Jim Mustian on Twitter, @JimMustian.

This article was amended May 29, 2014, to correct a reference to Simerman’s testimony about the FBI spotting an error in a graphic presented to agents before the reporters published the Hankton story. When Simerman said the FBI “caught our mistake” on a draft of a graphic outlining the alleged criminal operation of Telly Hankton, he was referring to an incorrect photograph of Gerard Howard — not the reporters’ inclusion of Bryan “Baby” Williams in the graphic.