Parliament is the supreme law making body and the Constitution doesn't give the Supreme Court of Pakistan the authority to strike down any constitutional amendment made by the Parliament. The current Constitution however gives the Supreme Court (or the Federal Shariat court) a conceptual support to strike down any laws that are repugnant to Islam, but the Parliament being the supreme law making body (if needed) can make fundamental changes to the structure of the Constitution and remove the clause that gives the Courts such an authority.