The standing of natural and legal persons to bring annulment proceedings is one of the most difficult and controversial issues in EC law. Article 173(4) EC states that non-addressees of a Community decision can only challenge it if they are directly and individually concerned by it. In Plaumann v. Commission (Case 25/62 [1963] E.C.R. 95) the Court explained that a decision is of individual concern to non-addressees if it “affects them by reason of certain attributes which are peculiar to them or by reason of circumstances in which they are differentiated from all other persons, and by virtue of these factors distinguishes them individually just as in the case of the person addressed”. But what degree of factual or legal differentiation must an applicant show to be individually concerned? The standard test is that the applicants need to belong to a “closed category”, namely one the membership of which had become fixed and ascertainable when the measure in question was adopted. The mere capacity of an applicant as a trader, importer or exporter does not suffice to render him individually concerned (Case 38/64 Getreide-Import Gesellschaft v. Commission [1965] E.C.R. 203; Case 191/89 Co-Frutta v. Commission [1989] E.C.R 793).