This paper attempts, on the one hand, to reveal the main principles of Competition Law (regulatory and case law framework) covering the prevention of parallel trade, mainly the prohibition of parallel imports, and on the other hand to cast light on the main effects of parallel imports prohibition imposed by an upstream supplier on the competitive structure of the downstream market. Especially, the regulatory framework that relates to Block Exemption Regulation 330/2010, (ex Block Exemption Regulation 2790/99), with Block Exemption Regulation 461/2010 (ex Block Exemption Regulation 1400/2002) in order to determine whether prohibition of parallel imports constitutes a hardcore restriction or not, while the economic analysis evaluates it in a geographical vertical market with upstream suppliers and downstream buyers which sell goods to the final (domestic) consumers. Administrative anticompetitive measures are considered as well. The results indicate that the prohibition of parallel imports by upstream firms cause vertical restraints to the domestic customers of the buyers.