Origin of blue law
1781, severe Puritanical code said to have been enacted 18c. in New Haven, Connecticut; of uncertain origin, perhaps from one of the ground senses behind blues, or from notion of coldness. Or perhaps connected to bluestocking in the sense of "puritanically plain or mean" (see bluestocking, which is a different application of the same term; the parliament of 1653 was derisively called the bluestocking parliament). The common explanation that they were written on blue paper is not considered valid; pale blue paper was used for many old U.S. legal documents and there would have been nothing notable about its use in this case.
Laws that prohibit certain businesses from opening on Sunday or from selling certain items on that day. Blue laws often apply to bars and to alcohol sales. Originally enacted to allow observation of Sunday as a Sabbath, blue laws have come under attack as violating the separation of church and state. The courts, however, have upheld most blue laws, on the basis that their observance has become secular and promotes Sunday as a day of rest and relaxation.