Pat LaFontaine, NHL vice president of hockey development and community affairs and one of the leaders in the creation of the Declaration of Principles, received the letter on Tuesday and shared it publicly on Wednesday.
"We've got the Pope and all of faith supporting this initiative," LaFontaine said. "Pretty powerful."
The letter, which was signed by Cardinal Pietro Parolin, Vatican Secretary of State, read: "His Holiness Pope Francis was pleased to learn that an international group of hockey organizations has chosen formally to adopt the Declaration of Principles that emerged from last year's Global Conference on Sport at the Service of Humanity. His Holiness trusts that this significant gesture will inspire greater appreciation for the pivotal role played by sports and sportsmanship in training future generations to pursue personal excellence and to promote the spiritual values of teamwork, solidarity and mutual respect so necessary for the building of a more just and fraternal world."
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LaFontaine and Los Angeles Kings president Luc Robitaille were part of an NHL delegation representing hockey at the Sport at the Service of Humanity conference in October 2016, held at the Vatican.
By that point LaFontaine was more than a year into working on what became the Declaration of Principles, signed Wednesday by organizations ranging from the NHL and the NHL Players' Association to Hockey Canada, USA Hockey and the International Ice Hockey Federation.
"What [Pope Francis] was asking the sports world to do is what we were already working on," LaFontaine said Wednesday. "So when I came back to brief [NHL Commissioner] Gary [Bettman], I said Gary, what's really exciting is this is giving me more confidence that the path we're on has been endorsed by the Pope and the world leaders of faith."