NEW DELHI: The Supreme Court today asked the Centre to respond to a plea of BJP leader Subramanian Swamy challenging constitutional validity of two penal provisions relating to the offence of defamation.A bench of Justices Dipak Misra and Prafulla C Pant also asked senior advocates K Parasaran and TR Andhyarujina to assist it as amicus curiae in the case.Swamy, against whom criminal defamation cases were filed in Tamil Nadu allegedly at the instance of former Chief Minister and AIADMK supremo J Jayalalithaa, has sought setting aside of sections 499 (defamation) and 500 (punishment for defamation) of the IPC The plea has said the IPC provisions put unreasonable restrictions on people's right to free speech and expression guaranteed under Article 19 (1) (a) of the Constitution.After brief hearing, the bench today asked Law Ministry , Tamil Nadu government and others to respond to the plea of Swamy within four weeks and listed it for hearing on July 7.Referring to rival contentions, it said, "it has been contended that Article 19 (2) of Constitution itself imposes reasonable restrictions (on freedom of speech and expression) and therefore, submission by Swamy that sections 499 and 500 of the IPC are beyond Article 19 (2) is unsustainable..."At this juncture, we thought it apt to ask senior advocates K Parasaran and TR Andhyarujina to assist court."Andhyarujina, who was present in the court room, told the bench that there has to be a debate on "conceptual meaning" of defamation and definition given to it (defamation) in the IPC.The bench said, "this case has tremendous repercussions" warranting appointment of amicus curiae as Swamy has raised issues relating to concept of free speech and expression."What is troubling us is that when at any time you read the provision of defamation/incitement to an offence what does it actually mean," it said.The BJP leader also submitted there is an international convention to de-criminalise defamation.Five defamation cases were filed against Swamy by the state government after he had allegedly made some allegations against Jayalalithaa on social sites.The apex court had stayed the proceedings in all the five cases in Tamil Nadu courts.