The International Regulations for Preventing Collisions at Sea 19721 are the latest version of the rules which regulate the exercise of the right of navigation at sea. The first international set of rules was laid down by the Brussels Convention, 1910.2 Previous to that, the rules were the creatures of unilateral United Kingdom legislation, although their content was understood to be a codification of the customary practices of good seamanship.3 The successive versions of the Collision Regulations have become increasingly detailed to cover situations previously unprovided for and to take into account technical developments in the size and manoeuvrability of ships and in the aids to navigation, particularly radar. The basic structure of the regulations has, though, changed little nor has the manner of their enforcement. Since the divorce of the regulations from the Safety of Life at Sea Convention when the 1972 rules were agreed, the international obligation on a State is “to give effect” to the substance of the rules. The manner of the discharge of this obligation has not been consistent. The U.K. is one of many, but by no means all, States for which the infringement of the regulations may be a criminal offence,4 the pattern of enforcement prevailing before the internationalization of the regulations persisting. Violation of them is made a criminal offence by the Merchant Shipping Act 1894, s. 419(2) requiring “wilful default” of the owner or master but, while obedience to them is enjoined by s. 419(1), violation of itself raises no presumption of civil liability, the standard for that being actual negligence.5 In fact, criminal prosecutions for breach of the regulations have been rare but there have been no suggestions that this sporadic recourse to the criminal sanction has fallen below what is required of the U.K. by international law.6 Since criminalization of breach of the regulations is not certainly required by the international agreement, it would be hard to argue that random or minimal enforcement of a State’s criminal law fell short of what international law requires so