ancient lights
noun /ˌeɪnʃənt ˈlaɪts/
/ˌeɪnʃənt ˈlaɪts/
[uncountable]- (in English law) the principle that you have the right to receive light through any window that has been there for 20 years or more. It may be used in cases where a person wants to build something in front of your house, etc.