The Code of Criminal Procedure, 1973 (CrPc)
92. Produce as to letters and telegrams.
(1) If any document, parcel or thing in the custody of a postal or telegraph authority is, in the opinion of the District Magistrate, Chief Judicial Magistrate, Court of Sessions or High Court wanted for the purpose of any investigation, inquiry, trial or other proceeding under this Code, such Magistrate or court may require postal or telegraph authority, as the case may be, or deliver the document, parcel or thing to such person a the Magistrate or Court directs.
(2) If any such document, parcel or thing is, in the opinion of any other Magistrate, whether Executive or Judicial, or of any Commissioner of police or District Superintendent of police, wanted for any such purpose, he may require the postal or telegraph authority, as the case nay be, to cause search to be made for and to detain such document, parcel or thing pending the order of a District Magistrate, Chief Judicial Magistrate or Court under sub-section (1)..