In 2009, he sent a photo crew to interview right-wing Knesset members, posing as students. Oppenheimer admitted that he was behind the act and that the Knesset officer filed a complaint against him against the police for impersonation. As a result, Oppenheimer was banned from entering the Knesset compound by then Speaker of the Knesset Reuven Rivlin. Oppenheimer announced that there had been a misunderstanding, and that Peace Now would not repeat such actions in the Knesset. As a result, Rivlin later renewed Oppenheimer's entry permit.
