The CL is a UEFA tournament and Turkish and Israeli teams can compete in it. It is, therefore, not an EU tournament or even a European tournament in that sense. Normally, one would expect that questions of law affecting such a tournament would refer to points of football law and here FIFA and UEFA would be authoritative. FFP, however, raises genuinely legal issues. The football authorities have tried to ensure that any questions arising from the decisions of the AC should be dealt with by CAS but this has been found a violation of human rights recently by a Brussels court. Clubs have accepted the ruling of CAS, though some have pursued the matter further in the Swiss courts. The interesting question would have been if Fenerbahce had not got satisfaction in the Swiss courts would it have pursued the matter in the ECJ or the Turkish courts? Now, one of the main arguments put forward by the leave campaign in the UK was that leaving the EU would "free the UK from having to accept the decisions of the ECJ". If City do call the legality of FFP into question it will almost certainly do so through the ECJ for a judgement UEFA would have to obey, but such a judgement would not necessarily have any force in the UK and a case filed in the English and Welsh courts may be necessary to pursue the letter writers, especially for damages. But for damages - a favourable judgement from the ECJ would render FFP null and void.