Apple Chief Executive Steve Jobs, who is out on medical leave, has been ordered by a federal magistrate to answer questions from plaintiffs’ lawyers in an antitrust lawsuit related to his company’s iTunes business.

U.S. Magistrate Judge Howard Lloyd, based in San Jose, Calif., ruled that lawyers representing the plaintiffs in the suit may question Jobs for a total of two hours. He issued the ruling Monday.

Apple could appeal the ruling to a district judge, but it would likely have to make a case that the magistrate “made a big mistake,” said Professor David Levine at University of California Hastings College of the Law.

An Apple spokeswoman declined to comment, and attorneys for the plaintiffs did not respond to requests for comment.

“The court finds that Jobs has unique, non-repetitive, firsthand knowledge about Apple’s software updates in October 2004 that rendered the RealNetworks’s digital music files once again inoperable with iPods,” Lloyd wrote in his ruling.

The ruling comes amid intense questions about Jobs’ health and whereabouts.

Earlier this month an energetic but thin Jobs resurfaced to unveil Apple’s new iPad 2.