green light district

noun

an area in which prostitution is officially tolerated

Word Origin for green light district

C21: from green light, modelled on red-light district
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012