AG Villalón has opined that Belgian legislation relating to deductibility of expenses was an infringement of Article 49 EC (freedom of services). The legislation restricted the ability of Belgian companies to deduct business expenses paid to suppliers established in other Member States, where that supplier would be subject to a more advantageous tax treatment on the income than an equivalent Belgian supplier unless the taxpayer could show that the transaction was "genuine and proper".

AG Villalón found that this was a restriction which was unjustified by the need to combat fiscal evasion. A Belgian taxpayer could not be expected to know whether its supplier were subject to a significantly advantageous tax regime (and was therefore incompatible with legal certainty), and the legislation was not restricted to a "related party" situation where fiscal evasion could be expected to pose a higher risk.