As per case facts, the State of Punjab appealed acquittals where arrests, searches, and seizures under the Narcotic Drugs and Psychotropic Substances Act, 1985 (NDPS Act) were deemed illegal due ... to non-compliance with statutory provisions. Conversely, convicted accused challenged their convictions on similar grounds, arguing that procedural irregularities during arrest and search vitiated their trials. The State contended that police acted under Cr.P.C. on reasonable suspicion, and NDPS Act provisions might not always apply strictly or be entirely mandatory. The question arose whether non-compliance with NDPS Act provisions governing arrest, search, and seizure makes the proceedings illegal and vitiates convictions, and how to distinguish between mandatory and directory provisions. Finally, the Supreme Court ruled that certain NDPS provisions, like those requiring an empowered officer for warrant issuance (Section 41), written record of prior information (Section 42(1)), recording grounds for sunset-to-sunrise search (Proviso to Section 42(1)), sending reports to superiors (Section 42(2)), and informing the accused of their right to be searched before a Gazetted Officer or Magistrate (Section 50), are mandatory, and non-compliance vitiates the trial. However, Cr.P.C. provisions (Sections 100, 165) are generally directory, and non-compliance might only amount to an irregularity, affecting evidence appreciation but not necessarily vitiating the trial unless prejudice is proven. Sections 52 and 57 (post-arrest/seizure steps) are also directory.