For how many years Britain did not enforce British laws in American colonies what is the name of the policy

Salutary Neglect, is the right answer.

Explanation:

The British administration supported an absolute policy of Salutary Neglect in the colonies that affected Massachusetts throughout the 18th century. This policy was a prearranged lack of implementation by the British rule of British trade ordinances in the communities of America. This system was chosen to ease the implementation of stringent laws, in particular, the commerce laws, imposed on the communities of America.

The correct answer is salutary neglect. The name of the policy came from a speech that the philosopher Edmund Burke gave to Parliament in the 1700s. A policy then emerged wherein the colonies were, more or less, left alone. Certainly more than they would have been as a subservient colony to the Crown.