He studied law and started his legal practice in Iran at the age of 24. The National Spiritual Assembly asked him to defend the oppressed Bahá'ís of Sháhrúd, where, on 8 August 1944, three friends had been martyred and 17 Bahá'í homes had been plundered and set on fire. 'Aziz defended them with great eloquence and undaunted courage, braving the vicious opposition of the clergy. Later he was asked to defend the Bahá'ís of Shiraz and still later those in Yazd. His unceasing endeavours won him the praise of the beloved Guardian who later designated him the "Shield of the Cause of God" and predicted that future historians would study his achievements.

In 1953 he and his wife Shamsi pioneered to Monte Carlo in Monaco to replace Mrs French who had passed away. While at this post he studied international law at the University of Paris-Sorbonne. In 1955 the Guardian appointed him to the Commission that appealed to the United Nations in Geneva and New York about the Iranian attempt to exterminate the Bahá'í community. In 1962 he became involved with the imprisoned Bahá'ís in Algeria and Morocco.

In 1968 Dr. Navidi became a representative of the Iranian Oil Company for its operations in the Indian Ocean and the family made their new home in Mauritius from where he worked to secure legal recognition of several of the new National Assemblies in the Indian Ocean region as he did with various African states. He fearlessly visited countries hostile to the Bahá'ís with no protection except his faith and his credentials as official lawyer to the Universal House of Justice with special status at the United Nations. His missions took him to Cameroon, the Central African Republic, Chad, the Congo, Gabon, the Gambia, Kenya, Madagascar, Senegal, Sierra Leone, Zaire, and many, many other countries throughout the world. He was successful time and again in persuading democratic governments and dictators alike to alter their laws and constitutions and to officially recognize the Bahá'í Faith. [BW20p866; Navidi, Dr. Aziz (1913-1987): Intrepid Pioneer, Knight of Bahá'u'lláh by Graham Walker; KoB341-344]

The Guardian, in a message to the Bahá'ís of the World dated 27 November 1954, written after the expropriation of the plot of land owned by the Covenant-breaker Farahangiz Khanum, (the daughter of Mírzá Asadu’llah Isfahani, sister of Fareed and wife of Sydney Sprague) who had refused to sell for more than thirty years, said that the way was now clear to construct the International Archives Building. He went on to say,:

   The raising of this Edifice will in turn herald the construction, in the course of successive epochs of the Formative Age of the Faith, of several other structures, which will serve as the administrative seats of such divinely appointed institutions as the Guardianship, the Hands of the Cause, and the Universal House of Justice. These Edifices will, in the shape of a far-flung arc, and following a harmonizing style of architecture, surround the resting-places of the Greatest Holy Leaf, ranking as foremost among the members of her sex in the Bahá’í Dispensation, of her Brother, offered up as a ransom by Bahá’u’lláh for the quickening of the world and its unification, and of their Mother, proclaimed by Him to be His chosen “consort in all the worlds of God.” The ultimate completion of this stupendous undertaking will mark the culmination of the development of a world-wide divinely-appointed Administrative Order whose beginnings may be traced as far back as the concluding years of the Heroic Age of the Faith.
   This vast and irresistible process, unexampled in the spiritual history of mankind, and which will synchronize with two no less significant developments—the establishment of the Lesser Peace and the evolution of Bahá’í national and local institutions—the one outside and the other within the Bahá’í world—will attain its final consummation, in the Golden Age of the Faith, through the raising of the standard of the Most Great Peace, and the emergence, in the plenitude of its power and glory, of the focal Center of the agencies constituting the World Order of Bahá’u’lláh. The final establishment of this seat of the future Bahá’í World Commonwealth will signalize at once the proclamation of the sovereignty of the Founder of our Faith and the advent of the Kingdom of the Father repeatedly lauded and promised by Jesus Christ. [Messages to the Bahá'í World p74-75]

In a message to the Project Manager of the Mount Carmel projects dated 31 May 1987, the Universal House of Justice indicated that "...the institutions mentioned by the beloved Guardian in the passage in which he spoke of the completion of the Arc being contemporaneous with the establishment of the Lesser Peace did not include the Library. And there is no reason in principle why it should not be constructed at a later date." In addition, given the proximity of the International Teaching Centre to the future site of the International Bahá'í Library, if they were to be constructed simultaneously it would further congest an already busy building site and access to the Seat of the Universal House of Justice. [Vineyard of the Lord No 4 July 1994 p8]