John went by the name of Wu Ching-hsiung until his conversion, when he was baptized John.

Graduating with honors from the Suzhou Comparative Law School of China in Shanghai, in 1920, Mr. Wu went to the University of Michigan Law School, where he received the degree of Doctor of Jurisprudence in 1921. Later he did graduate work at the Sorbonne, the University of Berlin and Harvard University Law School. He maintained a correspondence with U.S. Supreme Court Justice Oliver Wendell Holmes Jr., from his time as a student, and later produced scholarly work examining Holmes' legal thought.

He has honorary degrees from Boston College, St. John's University and the University of Portland.

Previously a Methodist, he was a convert to Roman Catholicism after reading Thérèse of Lisieux's biography.

Wu served as an adviser in the Chinese delegation to the 1945 United Nations Conference on International Organization in San Francisco and served as the Chinese ambassador to the Vatican in 1947-49. In 1957, Wu was appointed a judge of the Permanent Court of Arbitration in the Hague. After the Chinese Communist Revolution, Wu worked as a professor at the Seton Hall University School of Law in New Jersey until retiring to Taiwan in 1967.