The Navigation Act 1651
The first Navigation Act was passed by the Rump Parliament in October 1651 in the wake of an unsuccessful diplomatic attempt by Oliver St John and Walter Strickland to negotiate an alliance between the English Commonwealth and the United Provinces of the Netherlands. St John himself is said to have proposed the Act, in retaliation for the humiliation of his failed diplomacy.
Although the Navigation Act made no distinction between nations, it was understood to be aimed primarily at the Dutch. It stipulated that goods could be imported into territories of the English Commonwealth only by English ships, or by ships of the country originally producing the goods being carried. This was intended to cripple the freight trade, upon which Dutch commerce depended. Dutch ships would only be able to import the produce of Holland (primarily butter and cheese) into England and her colonies. The Dutch fishing industry was also affected because the Act stipulated that salt-fish and fish-oil could only be imported or exported from Commonwealth territories in English vessels.
The Act increased tension between the Commonwealth and the United Provinces and was a contributory factor in bringing about the First Anglo-Dutch War of 1652-4.
The Navigation Act was one of the few pieces of legislation from the Commonwealth era that continued after the Restoration, when it was actually extended to forbid exports as well as imports in foreign ships. Further Navigation Acts imposing various trade restrictions were passed throughout the colonial period of the 18th century.
S.R. Gardiner, History of the Commonwealth and Protectorate vol. ii (London 1903)
The Navigation Act 1651 full text, www.constitution.org