Chief Justice John Roberts has sold his shares of Pfizer Inc., a move that allows him to participate in two pending Supreme Court cases involving the pharmaceutical maker.

Federal law requires judges to sit out cases if they own even a single share of stock in any of the parties to a lawsuit. In the past, Roberts has not taken part in cases involving Pfizer because he owned less than $15,000 of the company’s stock, according to his latest report of personal finances, which covered 2009.