"I've always believed it was an important document in our country. Therefore, I'm privileged to be the owner," Rubenstein told the New York Post, adding he plans to display the copy, the only one from the era in the United States, at the National Archives. A total of seventeen copies are known to exist, the BBC said.
"I thought it was very important that the Magna Carta stay in the U.S.," Rubenstein said. "I feared it would escape and go to another country."
Britain's King John was forced to sign the Magna Carta, which curbed the power of the British monarchy and inspired the framers of the U.S. Constitution, in 1215.
The copy Rubenstein bought was placed on the auction block by former presidential candidate Ross Perot, who plans to donate the proceeds from the sale to his charitable foundation, the Post said.
The document dates back to 1297, the year the Magna Carta was enacted as law.