We advised an association of patients whose hemophiliac members established in Luxembourg received treatment in an establishment in Germany on the basis of a prior authorization issued by the Luxembourg social fund. Back in their host country, they asked to be reimbursed for drugs bought en masse in Germany on prescription from a doctor established in that country. The question arose as to whether the Luxembourg authorities were authorized to refuse them this reimbursement on the grounds that these products were also available in Luxembourg, even though they were cheaper in Germany than in Luxembourg. The answer to this question varies depending on whether you are under the regime of Regulation 883/2004 on the coordination of social security systems or under the regime of Directive 2011/24 on cross-border care.