Vick won The Associated Press Comeback Player of the Year award this past season, his second in the NFL since serving 18 months in prison for operating a dogfighting operation.
Mayor Pro Tem Dwaine Caraway presented the key at a ceremony in Dallas last week.
In a statement issued Monday, Mayor Tom Leppert distanced himself from the gift.
"The action taken was not sanctioned by my office and was not an official ceremonial honor on behalf of the city of Dallas," he said.
He said "official keys to the city" are presented by the mayor or an elected official designated by the mayor and are reserved for "an elected official of international status."
"Clearly, this was not the case in this situation and one without my knowledge or approval," he said.
In his own statement, Caraway said the key was "ceremonial." "These ceremonial gifts are different from the official keys to the city presented by the mayor," he said.
As for honoring a convicted felon, Caraway said, "I care deeply about animals" and "am deeply sorry to offend anyone who loves animals."
He acknowledged Vick's past but noted that "since making some bad choices, Michael Vick has devoted time to speaking to children about staying in school staying away from drugs, making positive choices about picking friends and the importance of education. That was the focus of the event."
Leppert said he has asked the city manager to "propose guidelines to prevent this situation in the future. Caraway said he would "welcome a clarification of the guidelines."
