[5][6] After practising law for several years, he was appointed King's Counsel in 1946 and became a judge at the South African Supreme Court in 1955.
Kuper sat in the Transvaal Provincial Division,[1] which covers Pretoria, South Africa's administrative capital.
In 1946, Kuper provided evidence before the Anglo-American Commission of Inquiry on Palestine, on behalf of South African Jews.
[2] At the February 1954 Conference on Jewish Material Claims Against Germany, Kuper represented South African Jews, together with Abel Shaban.
[2] Kuper's resignation from the chairmanship of the latter, which was made to pursue his career at the Supreme Court, was honoured by a pledge to plant a grove of 1,000 trees in Israel.