His journey in the judiciary progressed with him serving as the Allahabad High Court Judge in 1947 and then the Chief Justice of Rajasthan in 1951.Apart from the roles of a judge in the strict sense of the judiciary, he also chaired various commissions like Uttar Pradesh Judicial Reforms Committee in 1950. Then Indore Firing Inquiry Commission in 1954 and Dholapur Succession Case Commission in 1955.Further, he also was a member of the Law Commission in 1955.
In 1967, he was appointed as the CJI and succeeded J. K Subba Rao. In this position, he served for ten and a half months before retiring in 1968. To continue in his office after him, he had recommended the name of Amar Nath Grover from the Punjab and Haryana High Court.
One of his key works which still holds relevance is the report he submitted along with his committee. This report deals with the establishment of the capital city when there was a territorial dispute between Rayalaseema and Coastal Andhra Pradesh in 1953. This was the time when Andhra Pradesh had reorganized its boundaries by separating from the state of Madras. Due to this dispute, the Union Government at the time, had constituted this committee under the leadership of Justice Wanchoo to resolve it. Recently, when the bifurcation of Telengana from Andhra Pradesh too place,this committee report was reffered.
Another important work of J. Wanchoo which is a precedent on the current legal situation of Art.370 abrogation is his ruling over the validity of Art. 35A.This judgment came in 1961. Art 35A was incorporated by the order of President in 1954. This article provided for the special rights of the permanent citizens of Jammu and Kashmir over matters of government employment, acquisition of immovable property, settlement in the state, grant of scholarship and any such form of aid to be arranged by the State Government.
J. Wanchoo along with other judges held in this case, "Article 370 clearly recognises the special position of the state of J&K and that is why the President is given the power to apply the provisions of the Constitution to that state subject to such exceptions and modifications as the President may by order specify,” and thus, the presidential order was upheld.
Another important but later overturned judgment of J. Wanchoo was delivered in 1967. The case was on Aligarh Muslim University’s status as a minority institution.The court held that since the preamble of the 1920 AMU Act had stated that ‘whereas it is expedient to establish a Moslem University at Aligarh’ it becomes clear that it is a state university and therefore cannot enjoy minority status. However, this Judgment was overturned by subsequent judges who noted the need for protection of minority rights.