SA Constitution -
Everyone is equal before the law
ie one law for all, no exceptions based on religion.
The law is something that's flexible and is allowed to change to accomodate new circumstances, including exceptions for religion.
The constitution allows freedom of practicing religion, which doesn't necessarily have to do anything with the law.
BUT it also does not prevent legislation which recognises aspects of religion
(3) (a) This section does not prevent legislation recognising—
(i) marriages concluded under any tradition, or a system of
religious, personal or family law; or
(ii) systems of personal and family law under any tradition, or adhered to by
persons professing a particular religion.
(b) Recognition in terms of paragraph (a) must be consistent with this section and
the other provisions of the Constitution.
I'm guessing the whole recognition of Muslim marriages case is with regard to point b then.
So while everyone is equal before the law, the law is always something that can be changed to accomodate cultures and religion.