blue law
USA TODAYから表現を拾います。
States set sights on lifting Sunday hunting bans
But hunting "blue laws" also have their defenders, especially those concerned about property rights and quiet Sunday meals.
ASHEVILLE, N.C. — Lawmakers and hunting advocates in North Carolina and three other states are working to change "blue laws" that ban hunting on Sunday.
http://www.usatoday.com/story/news/nation/2013/04/27/states-sunday-hunting-bans-blue-laws/2115281/
blue lawが気になりました。青い等の意味で親しみのあるblueですが、辞書で確認してみるとここでは、「(道徳的に)厳格な」(『ジーニアス英和辞典 第3版』大修館)という意味になります。CDOでも調べてみると ‘a law that limits activities that are considered not to be moral for religious reasons, such as shopping or working on Sundays’とありました。ですので、blue lawで「厳格な法律」となるでしょうか。(Shou-VR*)