ABSTRACT
Such measures must be based on the personal conduct of the individual concerned. It does not have to be illegal, but a Member State must provide evidence that it has taken repressive or other effective measures to combat such conduct in order to rely on the derogation. What constitutes personal conduct was clarified by the ECJ in Case 41/74 Van Duyn in which the Court held that past association with an organisation does not count as personal conduct, although present association does.
