Judgement of the Court; 20 May 2010; in Case C‑111/09, Česká podnikatelská pojišťovna as, Vienna Insurance Group v Michal Bilas:

Article 24 of Council Regulation (EC) No 44/2001 of 22 December 2000 on jurisdiction and the recognition and enforcement of judgments in civil and commercial matters must be interpreted as meaning that the court seised, where the rules in Section 3 of Chapter II of that regulation were not complied with, must declare itself to have jurisdiction where the defendant enters an appearance and does not contest that court’s jurisdiction, since entering an appearance in that way amounts to a tacit prorogation of jurisdiction.