Bishop Bernard Fellay, head of the Society of Saint Pius X, told the magazine he had also barred Richard Williamson from making public appearances without his permission.
The British-born bishop "must now study the historical facts and correct his false statements," Fellay said. "The quicker the better."
He had "forbidden public appearances without authorisation," he added.
Fellay also said Williamson was ousted as the head of an Argentine seminary on January 31, 10 days after Swedish television broadcast an interview in which he said Nazis never used gas chambers and that only up to 300,000 Jews died in the Holocaust.
"I asked him right away, after I saw the interview, to correct this stupidity," Fellay said.
The television interview was conducted in November but broadcast on January 21, just three days before Pope Benedict XVI decided to lift Williamson's excommunication.
With the pope coming under widespread fire since the decision, the Vatican has said Williamson must "unequivocally and publicly" change his views before he can be admitted to office in the Church.
Williamson on Friday told Der Spiegel he would reexamine the historical evidence.
"If I find proof I would rectify (earlier statements)... But all that will take time," he said.
Williamson and Fellay were among four bishops whom the pope welcomed back into the flock in an attempt to heal a decades-old split with traditionalists who did not accept the reforms of the Second Vatican Council of the early 1960s.