The Italian law regulates production, trade and possession of narcotic drugs with Decree of the President of the Republic, 9 October 1990, no 309 
Updated text introduced by D.L. 20 March 2014, N. 36.

In Italy the law defines possession of narcotic drugs and psychotropic substances not punishable, when it is for personal use only.

The law punishes with imprisonment the possession of narcotic drugs for economic purposes (dealing).

The limit between detention for purely personal use or for dealing is very difficult to define.

To avoid risks in case of police control, never keep with you a quantity of substances exceeding what is needed for one day use and do not carry with you the substances that you intend to share with your friends. It is better that you divide the substances into doses ready for use. You have to claim that are prepared for your personal use.

Narcotic and psychotropic substances are listed in four tables annexed to decree 309/90. The tables are generally updated by Ministerial decree (published in the Official Journal of the Italian Republic “Gazzetta Ufficiale”) whenever the necessity arises, i.e. when: Lists of internationally classified substances such as narcotic or psychotropic are modified A substance becomes subject of abuse Some new drugs are introduced into the underground market When a new narcotic or psychotropic is recorded. Chems illegal market offers substances which have not yet been entered in the drug tables, because of their recent introduction in use. At this stage we talk about legal chems. It does not mean that these substances are not dangerous, not toxic and not giving dependence. These substances have only not yet been known enough. In National action plan for the prevention of diffusion of new psychoactive substances and the offer on the Internet – September 2013, Department of Anti-Narcotics – Italian Council of Ministers, we read: In recent years, the United Nations and the European Union, as well as important international research centers, have repeatedly reported about the unlawful market of Narcotic Drugs and synthetic Novel Psychoactive Substances (NPS), with highly dangerous pharmacological and toxicological features. Since 2009 the National Drug-Warning System of the Anti-Narcotics department has closely monitored the situation on the Italian territory by detecting about 280 new diffused substances. This market mainly uses the Internet to advertise multiple offers of new psychoactive substances, to collect orders and payments by credit cards and to ship them by normal postal carriers. The new NPS market goes parallel to that of counterfeit or illegal drugs, that now populate the Internet with offers equally dangerous to public health. In Italy, the National Early Warning System also detected about 70 cases of acute intoxication related to the intake of NPS that needed intensive care in emergency room. The National Early Warning System identifies the new psychoactive substances, detects its dangerousness and provides Health Ministry with information prior to their inclusion in narcotic drugs tables.