A blue law is a type of law in the Unite States and Canada designed to enforce moral standards, particularly the observance of Sunday as a day of worship or rest. Most have been repealed, declared unconstitutional or are simply unenforced, although prohibitions on the sale of alcoholic beverages, and occasionally almost all commerce, on Sundays are still enforced in many areas. Blue laws often prohibit an activity only during certain hours and there are usually exceptions to the prohibition of commerce, like grocery and drug stores. In some places blue laws may be enforced due to religious principles, but others are retained as a matter of tradition or out of convenience.