Warren and Kirk were slated to meet at Mohegan Sun Arena in Uncasville, Conn., in the Bellator 98 co-main event, but the Mohegan Tribe Department of Athletic Regulation deemed Warren ineligible to compete.
Bellator was unable to replace Warren, which forced Kirk (10-2) to be removed from the card.
Warren, a former Bellator featherweight champion, was seeking his second win in a row. He last fought in November, defeating Owen Evinger by unanimous decision. The win improved Warren to 8-3 as a pro.
The decision was made Friday morning after consultation with Mohegan doctor Michael Schwartz and neurologist Tony Alessi and was based on concern over Warren's health, and his inability to fulfill full medical licensing requirements.
"As of right now [Warren] has some things he needs to address, medically speaking," said Michael Mazzulli, the Mohegan Tribe's director of athletic regulation. "I gave [Warren] every opportunity to provide me documents and he was doing so, but the decision was made this morning."
Mazzulli said the decision would have been the same for any fighter on any card promoted at Mohegan. He said Bellator was understanding and respected Mohegan's concerns over fighter safety.