Effect on Trade between Member States: An element of competition procedure to be proved beyond any reasonable doubt or a notion to establish the applicable law?

The answer to the question posed in the title seems evident, if one looks at the function of the effect on trade between Member States within the framework of EU competition law. Simply put, and this is the essence of the notion, it aims to regulate the relationship between EU and national competition law, in particular it aims to provide direction for national competition authorities whether EU competition should be applied in a given case. If the effect on trade between Member States exists, national competition authorities shall apply EU competition law; if it does not, they do not have to.