Scotland had not suffered from the Navigation Act of 1651, which forbade foreign ships to import goods into England, or to trade with the colonies, or even to visit them without special leave. This statute was passed, in the words of Blackstone, “to punish our rebellious colonies, and to clip the wings of the Dutch.” It kept the colonial trade in the hands of England, and increased the value of English shipping. The terms of the Union during the Commonwealth had exempted Scotland from its provisions. But now the Union was at an end, and Scotland was once again a separate kingdom. The Parliament of England proceeded to pass a new and even more stringent Navigation Act, which inflicted a deadly blow upon the trade of Scotland.[93] Sir George Mackenzie traces the origin of this, and other laws hostile to Scottish commerce, to the fact that Clarendon and other English politicians were piqued by the way in which Lauderdale prided himself on having induced the king to withdraw the army from Scotland against their advice. “This excessive boasting,” he says, “that he had prevailed in this over Hyde, Middletoun, and all the English, did somewhat contribute to renew the old discords which had formerly been entertained between the two nations; and occasioned the making of those severe Acts, whereby the Parliament of England debarred the Scots from freedom of trade in their plantations, and from enjoying the benefit of natives in the privilege of shipping.”[94] The new law was so rigorous that no goods nor produce, of any country, could be imported into the colonies except from England or Wales. Irish goods could not go from Ireland, nor Scottish goods from Scotland. Moreover, the most important products of a colony could enter England, or another colony, only on payment of duty. English ships alone were allowed to carry goods to and from the colonies. The sugar, the tobacco, the cotton, in fact all the most useful produce of the colonies, could be shipped to England only, and could not enter an English port except in an English vessel. Nor could goods be imported into England from the continent of Europe except in English ships, or in ships belonging to the country which actually produced them. This monopoly, under which the colonies could trade with England alone, was a grievance to the colonies. They, however, had at least the privilege of trading with England. But to the colonial trade of Scotland the Navigation Act was ruinous.