Cameron J in My Vote Counts NPC v Speaker of the National Assembly  (CCT121/14) [2015] ZACC 31 (30 September 2015) at para [53] of minority judgment.

“These considerations yield the norm that a litigant cannot directly invoke the Constitution to extract a right he or she seeks to enforce without first relying on, or attacking the constitutionality of, legislation enacted to give effect to that right. [footnote omitted]  This is the form of constitutional subsidiarity Parliament invokes here.  Once legislation to fulfil a constitutional right exists, the Constitution’s embodiment of that right is no longer the prime mechanism for its enforcement.  The legislation is primary.  The right in the Constitution plays only a subsidiary or supporting role.”