“…Nazzini notes that AG Mazák suggested a different approach, with respect to refusal to supply, in particular (i) to look at the margin squeeze as a form of vertical foreclosure tactic similar to that carried out by refusal to supply, (ii) to take into consideration the risk that if there is not a duty to deal, "to impose a duty to charge upstream and downstream prices that allow as efficient downstream firms to compete effectively would reduce the dominant undertaking's investment incentives" and, most interestingly (iii) to take into consideration an "a fortiori", a very subtle, argument: if the duty to deal is not a pre-condition, and the company in theory could refuse to supply, "why can it not harm them by charging upstream and downstream prices that make it difficult for them to compete?" (R. Nazzini, cited, p 274 government and of the incumbent operator, the Commission's ability to use competition law to oversee the markets is necessary to ensure that markets are liberalised and incumbents are not protected by regulators" 94 . However, he also argued that the power of the EC and the application of competition law, in particular when NRAs act according to normative schemes set up by EU law in regulated sectors, should encounter a reasonable limit in line with a wider interpretation of the principles of subsidiarity, proportionality, legal certainty and loyal cooperation (all principles recalled by Telefónica's lawyers in the CFI appeal).…”