And in a case of resistance, to break open doors, chests, trunks, and other packages (see provisions in 1767 Townshend Acts).

Reason why Writs of Assistance were Introduced
As the American colonies grew in importance and profitability the British government attempted to make American trade profitable to British merchants by interfering in the government of the colonies. The colonists disobeyed the navigation laws and Britain 'turned a blind eye' due to its policy of Salutary Neglect. However, the benevolent period of Salutary Neglect all changed after the French and Indian War (aka Seven Years War 1755-1763) when the British were left with a massive war debt. To pay the war debt the British ended their policy of Salutary Neglect in the colonies. The British intended to end illegal trading, enforce the Navigation Acts and impose new taxes and the Writs of Assistance, or search warrants, would help them to do this.

The Use of Writs of Assistance
The British reversed their policy of Salutary Neglect but it was much easier to order the laws to be carried out than it was to implement them. It was almost impossible for the customs officers to prevent goods from being smuggled into the colonies. And equally difficult to seize them. The custom officers therefore asked the judges to give them writs of assistance to search the premises of suspects.