WASHINGTON — The Supreme Court ruled on Tuesday that a California woman injured in a train accident in Austria cannot sue in an American court. It was the Supreme Court’s first decision of the term in an argued case, and it was unanimous.

The woman, Carol P. Sachs of Berkeley, lost her legs after trying to board a moving train in Innsbruck. She said she should be allowed to sue the railroad in federal court in California because she had bought her Eurail pass in the United States on the Internet, from a travel agent in Massachusetts.

But Chief Justice John G. Roberts Jr., writing for the court, said the crucial events all took place in Austria, meaning the lawsuit must be filed there. “However Sachs frames her suit,” the chief justice wrote, “the incident in Innsbruck remains at its foundation.”

He quoted a 1915 letter from Justice Oliver Wendell Holmes Jr. to Felix Frankfurter, a law professor at Harvard who would later join the court. The crucial moment in a personal injury case, Justice Holmes wrote, is the “point of contact” — “the place where the boy got his fingers pinched.”