Grandfathered

Tom and Mary are grandfathered in at a lower rent for their apartment.

Toki Pona is grandfathered in as a language without an ISO 639-3 code at Tatoeba.

Tom is grandfathered in with an unlimited data plan.

When city fire codes were updated to modern standards, old historic buildings were grandfathered in. The museum that burned down in the historic district last week, for instance, completely lacked a fire sprinkler system, which was in part to blame for the massive loss of life.