Former FBI director Robert Mueller III’s report on the Ray Rice scandal offers a critical, but cautiously worded, assessment of the NFL and commissioner Roger Goodell. Most significantly, the report rejects the Associated Press’ contention that in April the NFL received a video of Rice hitting his then-fiancée, Janay Palmer, in a Revel Hotel elevator. Goodell has emphatically insisted that neither he nor anyone at the NFL had seen the video until it was released by TMZ last September. Mueller’s report prompted a ringing endorsement of Goodell from the NFL owners, his bosses. In a statement tonight on behalf of the 32 ownership groups, New York Giants president John Mara and Pittsburgh Steelers president Art Rooney II praised Goodell for being “forthright.” Goodell, whose decision to suspend Rice for the entire 2014 season was described by former U.S. District Judge Barbara Jones as “arbitrary” in her recent decision on Rice’s appeal, couldn’t have asked for a more favorable message from the one group to which he is truly accountable.

The Mueller report does find the NFL at fault on other grounds, albeit not grounds that would imply a scandal occurred or would jeopardize Goodell's future in the NFL. Mueller levies clear, but tempered, criticism in regard to the methodology and attitudes of NFL officials in interacting with the law.

• Mueller report: NFL didn't see Rice video before public

A cynic might conclude that the report’s relatively mild tone is consistent with the fact that its authors were attorneys hired and paid by the NFL. Along those lines, while the report's title references an “independent investigation,” the level of independence between an attorney and a client is necessarily limited.

These and other legal aspects of Mueller’s report are examined below.

Mueller’s report identifies structural errors in the NFL’s system for investigation

As alluded above, the report presents far from a glowing portrayal of the NFL and Goodell. It repeatedly criticizes the league for an ineffective system in investigating Rice and, more broadly, in investigating legal matters.

Most notably, the report finds the NFL at fault for adopting a passive approach in trying to obtain the elevator video. The report identifies the NFL’s deference to law enforcement as a contributing factor in failing to pursue and properly evaluate evidence. The report concludes by recommending that the NFL adopt policy changes, such as better training of NFL investigators and more stringent guidelines for investigations.

Key legal limitations of the investigation

Even with the best intentions, Mueller and his investigators, which included attorneys from the prestigious and NFL-connected law firm WilmerHale, faced substantial limitations in uncovering -- and publicly sharing -- the truth.

• The attorney-client relationship

When a company hires a law firm to investigate its practices, it does so with the understanding that the attorneys have ethical duties to advocate for the company’s interests. While the NFL has assured the public that Mueller had complete autonomy in his investigation, Mueller and his assisting attorneys were nonetheless working for the NFL. It would be naive to conclude that the report does not reflect this dynamic.

Mueller Report underscores Roger Goodell's deceit in Ray Rice case

Along those lines, there is reason to doubt that Mueller’s report would be written in a way that might enhance Rice’s wrongful termination grievance against the Ravens or advance the NFLPA’s lawsuit on behalf of Vikings running back Adrian Peterson. Put simply, attorneys do not make published statements that harm their clients’ legal interests. Mueller’s report, perhaps predictably, avoids these kinds of statements.

•Witnesses did not speak under oath

NFL employees and other witnesses who spoke with Mueller were not under oath. These witnesses therefore did not face the threat of perjury charges if they lied or exaggerated. In fairness to the NFL, witnesses may have felt an ethical duty to tell the truth. They also could have been worried about the employment consequences of lying to Mueller and Mueller realizing that he was told a lie.

Still, especially in light of the AP's detailed account of a female NFL official receiving the elevator video, some witnesses may have had incentives to lie in order to protect their employment. Ongoing questions raised about the accuracy of witness statements made to former FBI director Louis Freeh in his investigation into Penn State over the Jerry Sandusky scandal highlight this limitation.

• No subpoena power

It appears that Mueller conducted a thorough and perhaps exhaustive investigation. Mueller highlights how his team interviewed Goodell and more than 50 NFL employees who might have information about the elevator video. He also stresses that interviews were conducted with “every female employee, contractor, vendor, or intern whose electronic badge recorded that she was in the League’s main office on April 9, the date the alleged call was made.” As to physical evidence, Mueller points out that, “we collected, searched, and analyzed millions of documents, emails, and text messages from the League’s network.”

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The apparent completeness of the investigation does not mean it was complete. Independent investigators have no subpoena power. This means they cannot use a court order to compel a person to speak or to share physical evidence. It is unclear whether the lack of subpoena power limited Mueller’s investigation, but it is certainly possible.

• Investigation didn't begin for months​

On Sept. 10, 2014, Goodell announced that Mueller would lead an investigation. This was five months after the NFL allegedly received the elevator video and seven months after Rice injured Palmer. It is conceivable that some evidence may have been lost during the intervening months. Witnesses’ willingness to speak, as well as their recollection of events, may have also been harmed.

Compare this timing to how the NBA immediately investigated Donald Sterling following publication of his racially insensitive remarks. Within 72 hours, the league and its attorneys had interviewed every relevant witness and collected all the key documents. This enabled the NBA to quickly engineer a compelling legal strategy to ban Sterling and force him to sell the Los Angeles Clippers. Had the NBA waited weeks or months, it is very possible that some of the witnesses may have become unwilling to speak with attorneys retained by the NBA. Retrieving key evidence would have also become more difficult.

The NFLPA investigation into the Rice scandal will surely tell a different story

The NFLPA has no way of legally challenging Mueller’s report. The report is simply a public account of findings by investigators who were in a client relationship with the NFL. The report is not part of the collective bargaining relationship between players and owners, and the NFLPA is not in contract with Mueller.

The NFLPA, however, will likely offer its own report on the Rice scandal. The NFLPA launched its own investigation in late September led by Richard Craig Smith, a former prosecutor at the U.S. Department of Justice. To be sure, Smith and the NFLPA do not enjoy the same access to league officials and staff as did Mueller, nor do they have the same access to emails and other electronic recordings. The NFL could thus challenge the completeness of any report. Still, the NFLPA could offer a narrative far different from the one provided by Mueller and potentially damage Goodell’s reputation.

Examining the key issues entering Ray Rice's NFL appeals hearing

The Associated Press is limited in challenging Mueller

While Mueller’s report does not directly say the AP published a false story by reporting the NFL received the tape on April 9, it is difficult to read Mueller's report and not infer that accusation. Mueller found no evidence such a video was received and also stressed that the AP refused to cooperate with his investigation. The AP, for its part, claimed it listened to a voicemail from an NFL employee who said she was in receipt of the video. A law enforcement official who spoke with the AP on the condition of anonymity was the source. In a statement tonight to the Washington Post, AP executive editor Kathleen Carroll stressed, “We have reviewed the report and stand by our original reporting,” while noting the AP’s policy of not sharing reporters’ notes and sources.

Even if the AP would like to reveal its law enforcement source or assist the NFL, it is likely barred from doing so. First, and as Mueller recognizes in his report, the AP has a professional duty to preserve confidences. Not breaking a confidence is a basic tenet of journalism. Second, the law enforcement official could sue the AP if it cooperated with the NFL. Journalists who break their promises of confidentiality can be sued by outed sources in a “promissory estoppel” claim. This claim essentially means that a reporter cannot make a promise to keep information confidential and then later break it to the detriment of the person who shared the information.

The AP, in other words, may have no choice but to simply disagree with Mueller and leave it at that. Though it is unlikely, the law enforcement source could decide to come public and challenge Mueller and the NFL.

Michael McCann is a Massachusetts attorney and the founding director of the Sports and Entertainment Law Institute at the University of New Hampshire School of Law. He is also the distinguished visiting Hall of Fame Professor of Law at Mississippi College School of Law.