Seven months after a federal appellate court delivered a major setback to plans to open the nation’s first supervised injection site in Philadelphia, the nonprofit behind the endeavor is returning to court seeking new audiences and advancing new legal arguments. Safehouse attorneys announced they had filed a petition with the U.S. Supreme Court asking it to weigh in on whether plans to open a site designed to prevent overdose deaths by allowing people to take drugs under medical supervision run afoul of federal law. An adverse ruling from the high court could set back their cause for years on a national level, even as some states have advanced legislative efforts to approve them.