Sellers of Dr. Oz's new home in Pennsylvania say they 'insisted on' adding an unusual wrinkle

Pennsylvania GOP Senate nominee Dr. Mehmet Oz has shrugged off months of Democratic attacks that he's a carpetbagging out-of-towner by pointing to the house he and his wife bought last December in the well-to-do Philadelphia suburb of Bryn Athyn.

"I'm proud to own property in Pennsylvania," he has said on the trail when asked about the needling from his opponent, Lt. Gov. John Fetterman, over his longtime residency in New Jersey, where he lived before becoming a candidate.

The fine print of the deed to Oz's $3.1 million residence in Bryn Athyn shows a wrinkle, though -- one that an outside expert called "unheard of": If Oz ever needs to sell his new home, then the last owner gets right of first refusal to buy it back.

Half a dozen estate law experts told ABC News that the provision between Oz and the Academy of the New Church, which sold him the residence, was unusual for a residential transaction.

"It is unheard of in the residential setting," said Bob Tintner, a Philadelphia-based real estate lawyer, noting that the provision is seen mostly in commercial sales.

"It suggests to me that he's only here for a temporary period of time," Tintner said.

Oz's campaign cast it another way. "It's a beautiful property and they didn't want the property developed in any way that would harm the church," campaign spokeswoman Brittany Yanick told ABC News.

According to the deed, if Oz lists the home -- which sits on 34 verdant acres -- and receives an offer to purchase it, then the Academy of the New Church has the right to buy it back at the price offered by the prospective buyer.

"This doesn't give the church the right to buy back at any time. There has to be an offer made to Dr. Oz and his wife," explained Ken Milner, a real estate and corporate attorney in Philadelphia.

Reached by phone, the treasurer of the Academy of the New Church, Duane Hyatt, told ABC News that the church "insisted on" a right of first refusal in the Oz deal. Hyatt said it was something the organization typically does when it sells properties to ensure they are first in line to get it back.

Fetterman, Oz's Democratic opponent, has worked to turn Oz's relative lack of history in Pennsylvania into a major campaign issue, though voters in the state previously told ABC News they weren't all necessarily swayed by such attacks.

Some of the real estate experts told ABC News that while unusual in residential deals, the presence of the first-refusal clause did not imply anything nefarious.

Oz has personal ties to the Academy of the New Church's affiliated General Church of the New Jerusalem (also known as the New Church), a Christian denomination based on the works of the theologian Emanuel Swedenborg.

His wife's family includes "prominent members" of the church, the Philadelphia Inquirer reported in August, and his mother-in-law served on the church's board in 2008, according to church documents.

The experts who spoke to ABC News said the deed offered no proof of that. However, some said that the right of first refusal would likely make it "easier" for Oz to sell the property -- "in the sense that he knows he'll have a buyer," said Milner, the Philadelphia attorney.

Oz and his wife purchased the property last December, according to the deed of sale, a month after Oz announced his candidacy. It is a home "they have been hoping to buy for quite a while," Yanick, the campaign spokeswoman, told ABC News.

But the couple have yet to move in: They are staying with his in-laws and paying rent as he runs for Senate and renovates the new property.

"The renovations are ongoing. ... The house has a lot of history but it's going to take time," Yanick said. Oz plans to make it his permanent residence, she said.

"His wife's family has lived in Bryn Athyn for over 100 years," Yanick said. "The house they are currently living in is the house he and his wife were married in."

She declined to say whether the home had been on the open market when Oz purchased it.