In this fifth part in a series of reports on state aid, Mason explains that tax reductions violate Article 107 TFEU when they are selective rather than generally available to all taxpayers. Although selectivity doctrine is in flux, Mason describes the status quo and attempts to classify types of selectivity that the European Commission and EU courts have identified in prior cases. She analogizes judicial review of state aid by the EU courts to equal protection review by US courts, arguing that the EU courts implicitly use a tiers-of-scrutiny approach to analyzing state-aid cases. Under this approach, the courts' degree of scrutiny varies with kind of classification the state made in its aid measure, Suspect classifications--including those based on sector, region, size, residence, and engagement in cross-border commerce--receive strict scrutiny, whereas non-suspect classifications receive the EU-equivalent of only rational-basis review.
Ruth Mason, Special Report on EU State Aid: Part 5—An American View of State Aid, 157 Tax Notes 645–662 (2017).