"There's no place in the ministry of our church for anyone who would put a child in danger," Keeler said Friday.
The cardinal met for 90 minutes Thursday with Dontee Stokes, the 26-year-old Baltimore man who told police he shot the Rev. Maurice Blackwell on May 13 because he had been molested by the priest years earlier. He faces attempted murder charges.
"I apologized for the pain that he has suffered, and to him I renewed the offer of the archdiocese to assist with the counseling that, appropriately, he may require," Keeler said.
Keeler also told Stokes he would try to enact the policy at a conference of the nation's bishops in June in Dallas.
The meeting between Stokes and the cardinal took place at the home of Stokes' aunt, where Stokes has been under house arrest. Keeler said he found Stokes to be a thoughtful person and ended the meeting with a prayer.
Keeler, who spoke for less than two minutes on Friday, did not take questions from reporters.
Stokes faces attempted first-degree murder charges. He told police he shot Blackwell outside the suspended priest's home in Baltimore on May 13.
Keeler also has apologized to the Stokes family for reinstating Blackwell after Stokes accused him of sexual abuse in 1993. Keeler put the priest back into his parish at St. Edward Roman Catholic Church, going against a recommendation by his review board.
Blackwell lost his authority as a priest five years later, after he admitted to a long-term sexual relationship with another boy years earlier.
Blackwell has not been charged, but authorities have started new inquiries into the allegations.
In other developments:
The Milwaukee Archdiocese in 1998 paid $450,000 to a former theology student who accused Weakland of sexually assaulting him in 1979. Weakland denies ever abusing anyone.
During a prayer service Friday, Weakland said: ``I apologize to all the faithful of the archdiocese which I love so much, to all its people and clergy for the scandal that has occurred because of my sinfulness.''
The money for the settlement came from the archdiocese's general budget, which includes income from sources such as investments and church-owned rental property, the archdiocese has said.