Roberts a pivotal vote in the Supreme Court's big opinionsThe biggest cases of the Supreme Court term so far have a surprising common thread. On a court with five Republican appointees, the liberal justices have been in the majority in rulings that make workplace discrimination against gay and transgender people illegal, protect young immigrants from deportation and, as of Monday, struck down a Louisiana law that restricted abortion providers. As surprising, Chief Justice John Roberts, a conservative nominated by President George W. Bush who has led the court for nearly 15 years, has joined his liberal colleagues in all three.