Warships are designed for fighting in war. In peacetime, the primary task of warships and of their crews is to prepare for war. At the same time, because they are a visible embodiment of force, they may, at the pleasure of the executive, be employed on other tasks where the display of force is useful, such as the protection of sovereignty or the enforcement of laws both domestic and international. Some countries — the United States is an example — as a matter of principle, do not use warships to assist in the enforcement of national laws. Others, such as the United Kingdom and Canada, do use warships for such tasks. As a matter of practice, however, Canadian warships are rarely used for law enforcement against Canadian vessels.