grandfather sb/sth into sth
phrasal verb with grandfather verb LAW US uk/ˈɡrænfɑːðər/ us
(also grandfather sb/sth in) to allow someone to continue to do or to have something that a new law or rule makes illegal:
Most existing companies will be grandfathered into the old system for up to five years.
Many old bridges will suddenly be out of date but will be grandfathered in.