The US Supreme Court has unanimously rejected an effort to restrict access to the abortion pill mifepristone.The decision, which came two years after the court rescinded the nationwide guarantee to an abortion, was welcomed by pro-choice activists.The justices decided the plaintiffs, a group of anti-abortion doctors and activists, did not have a legal right to sue. But they left the door open to other attempts to limit the availability of the drug.Mifepristone is one of two drugs used in a medication abortion, now the most common method of terminating pregnancies in the US. The plaintiffs,…