The constitutional validity of the laws passed by the states and the parliament is decided by

According to the Constitution, Parliament and the state legislatures in India have the power to make laws within their respective jurisdictions. This power is not absolute in nature. The Constitution vests in the judiciary, the power to adjudicate upon the constitutional validity of all laws. If a law made by Parliament or the state legislatures violates any provision of the Constitution, the Supreme Court has the power to declare such a law invalid or ultra vires. This check notwithstanding, the founding fathers wanted the Constitution to be an adaptable document rather than a rigid framework for governance. Hence Parliament was invested with the power to amend the Constitution.
Article 368 of the Constitution gives the impression that Parliament's amending powers are absolute and encompass all parts of the document. But the Supreme Court has acted as a brake to the legislative enthusiasm of Parliament ever since independence. With the intention of preserving the original ideals envisioned by the constitution-makers, the apex court pronounced that Parliament could not distort, damage or alter the basic features of the Constitution under the pretext of amending it. The phrase 'basic structure' itself cannot be found in the Constitution. The Supreme Court recognised this concept for the first time in the historic Kesavananda Bharati case in 1973. Ever since the Supreme Court has been the interpreter of the Constitution and the arbiter of all amendments made by Parliament.