It’s official — history professor Anders Winroth has been dubbed a genius, and he has a $500,000 grant to show for it.

The MacArthur Foundation tapped Winroth Sunday as one of 24 MacArthur Fellows, each of whom receive an award commonly referred to as an unrestricted “genius grant.” Winroth was selected for his research in medieval canon law. The purpose of the fellows program is to encourage individuals with already impressive track records to make further contributions to society.

“It’s rather overwhelming to get a message like this,” Winroth said. “[There is] also a great responsibility to use it for good.”

Winroth said he may go on research leave next year and use the money, which he will receive over the course of five years, to study the teaching of the law in the 12th century.

History Department chairman Jon Butler called the award “a scholar’s dream.”

“I think it’s also a reminder of what stands at the heart of the university,” Butler said. “The independent pursuit of knowledge — that’s at base what the MacArthur Fellows recognize. [The awards are] not political; they’re not trendy. They recognize creativity in often-distant subjects because [the winners’] knowledge — restructures our view of whole huge chunks of the world.”

Many of the award winners are academics, but the avowed purpose of the grants is to recognize originality and creativity in any realm. Recipients included a photojournalist from Sierra Leone, a children’s book author from Ohio, and an artist-blacksmith from Sante Fe.

Winroth, a Branford College resident fellow, found that several manuscripts of Gratian’s “Decretum” — a foundational book of church law thought to be abridgements — were actually first editions. The “Decretum,” which deals with a variety of subjects ranging from marriage to legal procedures, had long been a source of confusion for medieval scholars.

“The award recognizes his solving of a major problem in church history and the history of ideas that have baffled scholars for over a century,” said Paul Freedman, director of Yale’s Medieval Studies Program.

Butler said Winroth’s work offers a major advance in the study of scholastic canon law.

“He really discovered the DNA of the founding document of medieval canon law, which is in turn the foundation of the western legal tradition,” he said.

Nominations for the MacArthur Fellows Program are anonymous. Winroth did not know he was in the running for the award until he received a congratulatory phone call from the foundation.

“I have no idea [who nominated me],” Winroth said. “The whole process is shrouded in secrecy.”

The members and workings of the final selection committee are kept secret as well. Anonymous evaluations from experts in the field are also considered in the selection process.

Butler declined to comment on whether he had advance knowledge that Winroth would be named a fellow.

According to one student, Winroth’s talents extend beyond his research and into the classroom.

“He is an entertaining and informative lecturer who seems genuinely delighted to be behind — or pacing next to — the podium every day,” Samuel Frank ’06, a student in Winroth’s “Early Middle Ages 284-1000” class, said in an e-mail. “He’s also approachable and friendly on a one-to-one basis.”

The MacArthur foundation, which gives approximately $175 million each year in grants, has been naming fellows since 1981.