The Supreme Court on Thursday issued four significant rulings, overturning a controversial Purdue Pharma bankruptcy plan that would have provided billions of dollars to help address the nation’s opioid crisis in exchange for protecting the family that owns the company from future lawsuits. It also ruled against in-house Securities and Exchange Commission tribunals, blocked an Environmental Protection Agency air-quality initiative while appeals continue and formally issued a decision allowing emergency abortions in Idaho while that case makes its way through the courts. Other decisions, including whether Donald Trump is immune from prosecution in his federal election-interference case, remain to be issued, and the court — which usually winds up its term in June — will be continuing into July.