His death was announced by Harvard Law School, where he had a teaching career of more than 50 years. The cause was pneumonia, said his identical twin brother, Robert B. von Mehren.
"He was a leading figure for many decades in comparative law and international conflicts of law and jurisdictions," said George A. Bermann, professor of law at Columbia University and a co-editor of the American Journal of Comparative Law, who called Professor von Mehren "the undisputed leader in these increasingly important fields."
Professor von Mehren was named Story professor emeritus of law in 1991 but continued to work until just before his death.
He was an authority on international jurisdiction, comparative law and international commercial arbitration. He studied law in three countries, taught it in nine, and published 10 books and hundreds of articles.
Professor von Mehren formerly headed the United States delegation to the Hague Conference on Private International Law, a standing body that writes the procedures for such dealings. Last year, he witnessed the completion of an agreement on international jurisdiction and the effects of foreign judgments in civil and commercial matters.
Arthur Taylor von Mehren was born in Albert Lea, Minn., and graduated Phi Beta Kappa from Harvard in 1942. He received his law degree from Harvard in 1945 and a doctorate in government a year later, when he was appointed an assistant professor at Harvard Law. Fluent in French and German, he spent the first three years of his career in Europe studying French, German and Swiss law.
His study comparing United States and German civil procedures remained a standard for 50 years. He was an editor for many years of the American Journal of Comparative Law and founded the Joseph Story fellow program under which young German academics worked as his research assistant for a year.
He was a member of the Advisory Committee on Private International Law at the State Department, and a founding member and past president of the American Society of Comparative Law.
Besides his brother, a resident of Manhattan, Professor von Mehren is survived by his wife of 53 years, Joan Moore von Mehren; three sons, George M., of Cleveland, Peter A., of Philadelphia, and Philip T., of Bronxville, N.Y.; and several grandchildren.