++++ Tax provisions - Harmonization of laws - Turnover tax - Common system of value-added tax - Tax on the supply of goods within the territory of a Member State - Application to unlawful traffic in narcotic drugs - Not permissible - Criminal sanctions for offences - Powers of the Member States - Policy of selective prosecution with regard to supplies of hemp-based drugs - Circumstance not justifying the imposition of tax ( Council Directive 77/388, Art . 2 )