A probate judge in Memphis ended an unusual legal arrangement on Friday between Michael Oher, a former National Football League player and the subject of the hit movie “The Blind Side,” and the people who took him in when he was a teenager, which had given them broad authority over Mr. Oher’s affairs.

Mr. Oher, 37, filed a petition in August to terminate the nearly 20-year-old conservatorship, claiming that he had been tricked into signing away his decision-making powers under the pretense that he would be adopted. The petition stated that Leigh Anne Tuohy and Sean Tuohy, with whom Mr. Oher started staying when he was 16, were given power of attorney and access to his medical records, and that he could not bind himself to any contracts without their approval.

The move by the judge was largely expected; the Tuohys had said at the time the petition was filed that they were happy to have the conservatorship end.

Based on the book by Michael Lewis, “The Blind Side” is one of the…