Another class of evidence adduced by the English authors refers to the impressment of ships for the defence of the realm or the transport of troops on occasions of emergency. These duties were at first performed by the vessels of the Cinque Ports, in accordance with their charters; but as early at least as the reign of Richard I., ordinances were issued (at Grimsby) regulating the mode of arresting vessels and men for the service of the king,[38] and it became an established and common practice. Numerous instances occur which show that on such occasions foreign vessels were not exempt from arrest, though compensation was at least sometimes made to their owners.[39] The argument of the English writers that these arbitrary proceedings were evidence of the dominion exercised by the kings of England on their sea is rebutted by the practice in France. Froissart[40] tells us that the French adopted similar measures in 1386 when they were preparing for an invasion of England, and the practice was doubtless common enough, and justified by the emergency which occasioned it. With regard to the most important attribute of maritime sovereignty--the right to exclude others from an equal use of a particular sea by prohibiting navigation, at least of vessels of war, and from fishing in it, or by imposing dues and conditions for the liberty--there is scarcely a scrap of evidence to show that any authority of the kind was exercised by England in the adjacent seas. The circumstance is noteworthy, inasmuch as other countries which then enjoyed undoubted maritime sovereignty, did not permit unrestricted navigation or fishing in the seas specially under their control, as Venice in the Adriatic, and Denmark in the northern seas and in the Baltic. The evidence concerning the liberty of fishing in the sea along our coasts is dealt with in another chapter, but it may be said here that this liberty was provided for in a series of treaties with other Powers. As for liberty of navigation, it was asserted, or rather implied, by Selden, in guarded language, that the kings of England anciently possessed the power of refusing it;[41] but the evidence relates for the most part to passports and safe-conducts “by land and sea,” and to the impressment of vessels, referred to above. There appears to be not a single fact to prove that the liberty of innocent navigation in the English seas was ever interfered with by the king. The Parliament of Ireland, it is true, passed an Act in 1465 prohibiting all foreign vessels “from going to fish at Ireland among the king’s enemies” without first obtaining a license, on pain of forfeiture of the vessel. But it is clear from the preamble that the Act was passed because foreign vessels frequenting the Irish coast for fishing were supplying the king’s enemies with money, arms, and provisions.