Steelers quarterback Ben Roethlisberger's six-game suspension signals a stricter approach to the way NFL commissioner Roger Goodell enforces player behavior.

Since the NFL amended its personal-conduct policy in 2007, Mr. Goodell has suspended 16 players, and Mr. Roethlisberger is the only one who was never arrested or charged with a crime.

"A six-game suspension sends out a pretty strong message, especially for someone who was not indicted, not arraigned and not charged," University of Central Florida professor and pro-sports consultant Bill Sutton said.

When Mr. Goodell became commissioner in September 2006, he inherited a league rife with criminal cases. At the time, the NFL had a 667-word personal-conduct policy that allowed punishment only when an NFL employee was convicted of a crime or had pleaded guilty or no contest to a crime.

Seven months later, Mr. Goodell crafted a 1,303-word policy, with the approval of the NFL Players' Association, that gave him the authority to punish employees even if they avoid a conviction, or as Mr. Roethlisberger learned Wednesday, even if they avoid an arrest.

"It is not enough simply to avoid being found guilty of a crime," the policy states. "Instead, as an employee of the NFL or a member club, you are held to a higher standard and expected to conduct yourself in a way that is responsible, promotes the values upon which the League is based, and is lawful."

In a letter to Mr. Roethlisberger explaining the suspension, Mr. Goodell wrote, "There is nothing about your conduct in Milledgeville that can remotely be described as admirable, responsible, or consistent with either the values of the league or the expectations of our fans."

Mr. Roethlisberger's six-game suspension is among the harshest sentences Mr. Goodell has administered -- only four players have missed more than four games because of a personal-conduct suspension.

Former Titans and Cowboys defensive back Adam "Pacman" Jones served a one-year suspension in 2007 when he faced felony charges in two states. Former Bengals receiver Chris Henry, who died in a motor vehicle accident in December, was suspended for eight games in 2007 following a two-year span in which he was arrested five times. Bengals defensive tackle Terry "Tank" Johnson, then playing for the Bears, received an eight-game suspension in 2007 after an arrest on gun charges. Ravens receiver Donte Stallworth, then playing for the Browns, was suspended indefinitely after pleading guilty to DUI manslaughter and missed the entire 2009 season.

Two players received indefinite suspensions, but they missed or will miss fewer than six games after serving jail sentences. Then a Falcon, Eagles quarterback Michael Vick was suspended indefinitely after a federal dogfighting conviction but missed only two games after his sentence. Former Steelers receiver Plaxico Burress is currently indefinitely suspended, but Mr. Goodell has said he will reinstate the receiver upon his release from jail for illegal gun possession.

Mr. Roethlisberger's suspension is conditional, meaning he could miss as few as four games or more than six, depending on the quarterback's cooperation.

Though Mr. Roethlisberger is the only suspended player with a clean criminal background, he is not the only player who was suspended after an incident in which no arrest was made.

Mr. Jones was suspended for four games in 2008 after an altercation with one of his security guards. No charges were filed in that case, but the suspension was Mr. Jones's second. The first followed multiple felony charges.

Mr. Sutton, a Pittsburgh native and associate director and professor at the DeVos Sports Business Management Graduate Program at UCF, said the personal-conduct policy gives Mr. Goodell power to protect the brand, or the "shield," in reference to the NFL logo.

"The NFL is the most successful sports league in the United States," Mr. Sutton said. "That's been built up over time. There's a lot of brand equity in that shield, and they are not going to let anybody demean that."

According to the San Diego Union-Tribune, which tracks NFL player arrests and major citations, incidents involving players have decreased since the policy was amended. There were 44 arrests and citations involving players from April 2009 to April 2010, down from 79 in the same 12-month period in 2006 and 2007.

"We believe the policy, which was developed with our players, has been effective in reducing the number of negative incidents," NFL spokesman Greg Aiello said. "The numbers bear out the fact that it is working, but it is an ongoing challenge that we have to continue to emphasize."

Mr. Sutton said the policy is impacting player conduct and added it sends a message to fans that the NFL does not accept criminal or obscene behavior.

Ralph Cindrich, a sports attorney and agent who represents Steelers linebacker James Farrior, said he is not sure if the policy had an impact on player behavior. But Mr. Roethlisberger's suspension "will make some players wake up," he said.

Mr. Sutton and Mr. Cindrich agreed Mr. Roethlisberger's suspension sends a message to players that the league does not discriminate when punishing its employees, though the same could not be said of the policy in the past. Mr. Roethlisberger is the most accomplished player suspended for personal conduct, and the second white player.

Mr. Sutton said he believed race was a factor, adding players were watching Mr. Goodell to see how he handled Mr. Roethlisberger. Would he be lenient on a two-time Super Bowl winner? Would he treat a white quarterback differently than a black lineman? Would he protect a superstar where he would punish a role player?

"The answer was no, no and no," Mr. Sutton said.

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