NFL owners Wednesday unanimously approved a revised personal conduct policy, commissioner Roger Goodell announced.

The new policy takes effect immediately. Among the key changes:

• The policy embraces the use of independent investigations. To that end, the NFL will hire a special counsel for investigations and conduct who will oversee initial discipline.

ESPN's "Outside the Lines" has obtained a copy of the memo sent by commissioner Roger Goodell to NFL owners, outlining the key points of the revamped personal conduct policy that was discussed and unanimously approved on Wednesday. • Personal Conduct Policy memo • Mission and Values statement

• The policy will implement an element of leave with pay during investigations of people charged with violent crimes.

• The commissioner will maintain a role in the appeals process but also may appoint a panel of independent experts to participate in deciding an appeal.

Goodell said Wednesday that the person hired to fill the special counsel role will be a "highly qualified individual with a criminal justice background."

"The person will oversee our investigations and decide the discipline for violations of the policy," he added.

After the Ray Rice and Adrian Peterson cases, a more extensive list of prohibited conduct will be included in the policy, as well as specific criteria for paid leave for anyone charged with a violent crime.

A six-game suspension without pay for violations involving assault, sexual assault, battery, domestic violence, child abuse and other forms of family violence will be in effect, but with consideration given to mitigating or aggravating circumstances.

"The policy is comprehensive," Goodell said. "It is strong. It is tough. And it is better for everyone associated with the NFL.

"I have stated it many times: Being part of the NFL is a privilege. It is not a right. The measures adopted today uphold that principle."

The NFL Players Association issued a statement in which it expressed its displeasure with not being able to collectively bargain changes to the policy.

"Our union has not been offered the professional courtesy of seeing the NFL's new personal conduct policy before it hit the presses," the union said. "Their unilateral decision and conduct today is the only thing that has been consistent over the past few months."

The union could consider Wednesday's vote by the owners as a violation of the collective bargaining agreement reached in 2011, giving the union cause to file a grievance.

Among the union's options is pursuing an unfair labor practice charge with the National Labor Relations Board. The players could argue this policy is a change in terms and conditions of employment; the National Labor Relations Act says such changes in unionized situations are subject to collective bargaining.

"I have stated it many times: Being part of the NFL is a privilege. It is not a right. The measures adopted today uphold that principle."

NFL executive vice president and general counsel Jeff Pash said the NFLPA's claim that it has not seen the policy lacks credibility because of the ongoing discussions between the league and the union.

"The union knows every element of what we've been talking about because we've talked to them about it already," he said. "I respect the fact that they may not agree with everything that's been done, and I respect the fact that there's an unfortunate [need] to react: 'They say X, so we will say not X.' But I think that the best thing for everybody would be to take a step back and recognize the issues of reputation, of standards, of conduct."

Troy Vincent, the NFL executive vice president of football operations and a former president of the NFLPA, said he is "ready to move on from the union and the statements."

"They've had ample amount of time to contribute to where we're going. It's always been that way," he said. "Farce, you hear the term farce, unilateral decisions -- they've been part of the process the entire time.

"The people who don't like discipline are those who have committed a criminal act. Nobody likes to visit the principal. That's a small number of players every year. Those are the ones who have a problem, whether it's the process, it's the amount of discipline or the fine."

Seattle Seahawks cornerback Richard Sherman, the team's player representative, echoed the union's criticism of the NFL's actions.

"I think it's interesting anytime you make changes to a policy that we collectively bargained for and you don't collectively bargain for it," he said. "So, like the [players association], said, it's [the NFL] doing it by the seat of its pants and making it up as they go along. You would hope anything having to do with that the players, we would have some say-so in the policy and at least something we could agree on and everybody is comfortable with. Obviously, that isn't what they saw fit."

Later Wednesday, Goodell sent a letter to fans on the new policy, also thanking them for their support of the league.

"Our communities are the heart of our teams and we put everything into making a positive impact on them. While we are stewards of the game of football, we know that virtue isn't earned on the field alone. Character and values sits above everything else because we represent something that means so much to so many people," he wrote.

The NFL tweeted out a link to a flow chart that explains how the new policy -- which applies to all league personnel (owners, coaches, players, other team employees, game officials and league office employees) -- works.

According to a description on the flow chart, under the new policy, "Clubs are obligated to promptly report any potential violation of the policy that comes to their attention and must fully cooperate with any related law enforcement and NFL investigations."

Arizona Cardinals owner Michael Bidwill was appointed to serve as chairman of a nine-member committee that will oversee the new policy, Goodell announced. The other owners on the committee are Arthur Blank (Atlanta Falcons), Clark Hunt (Kansas City Chiefs), Dee Haslam (wife of Cleveland Browns owner Jimmy Haslam), Robert C. McNair (Houston Texans), Charlotte Jones Anderson (Dallas Cowboys executive vice president) and George McCaskey (Chicago Bears).

Two former players with ownership stakes also will serve on the committee: Warrick Dunn (Falcons) and John Stallworth (Pittsburgh Steelers).

"Our union has not been offered the professional courtesy of seeing the NFL's new personal conduct policy before it hit the presses. Their unilateral decision and conduct today is the only thing that has been consistent over the past few months." NFL Players Association

"I think the commissioner asked me to chair this committee because of my background from 1990 to '96 serving as a federal prosecutor in Phoenix working in violent crimes," Bidwill said. "That background gives me a unique perspective on some of the issues we are facing."

ESPN's "Outside the Lines" obtained a copy of a memo, which outlined the changes to the revamped policy, and an attached mission statement sent by Goodell to the NFL's owners ahead of the vote. In the memo, Goodell writes that the league has decided it can "no longer defer entirely to the decisions of the criminal justice system, which is governed by processes and considerations that are not appropriate to a workplace, especially a workplace as visible and influential as ours."

Goodell says in the memo that he wants the NFL to "continuously review and refresh" its standards and policies. He stresses that the league can no longer completely defer to the courts in matters of domestic violence, child abuse and sexual assault, "all of which are complex and difficult subjects."

"Each is a societal problem that is frequently underreported," Goodell writes. "As a league, we must have a continued focus on the needs of victims and families; among other things, we must encourage victims and those who observe such misconduct to come forward, to report offenses, and to seek help."

In his memo, Goodell writes that the new nine-owner committee "will be responsible for ensuring that our Policy remains current and reflective of evolving legal and societal standards."

ESPN.com's Tim MacMahon and Terry Blount and The Associated Press contributed to this report.