A law restricting activities or sales of goods on Sunday, which stems from the accommodation of Christian Sunday worship. Many states continue the use of blue laws for the sole sake of tradition. Many states in the Southern United States still practice of these blue laws. These are called Blue Law States.
The blue law is usually referenced with respect to the prohibited sale of alcohol. However, it is often associated with the prohibition of any sales whatsoever.
"I hate Georgia; you can't buy any alcohol from 12AM Saturday to 12AM Sunday. How am I supposed to watch sports on Sunday without any beer? Damn blue laws."