Legal basis of the Sole Source
Directive 2014/24/EU of the European parliament and of the Council of 26 February 2014 on Public procurement and repealing Directive 2004/18/EC Art. 32 part 2b (ii and iii) and 3b allows state agencies to buy directly products and services without applying for the open tender procedure.
Art. 32 part 2b, II - competition is absent for technical reasons;
Art. 32 part 2b, III - the protection of exclusive rights, including intellectual property rights;
Art. 32 part 3b - for additional deliveries by the original supplier which are intended either as a partial replacement of supplies or installations or as the extension of existing supplies or installations where a change of supplier would oblige the contracting authority to acquire supplies having different technical characteristics which would result in incompatibility or disproportionate technical difficulties in operation and maintenance