grandfather clause

An exemption to a new law which accommodates already existing entities (metaphoric grandfathers) not having to comply. Eg: existing buildings not needing restructuring to accommodate new building / environmental codes. A law increasing the drinking age from 18 to 21 but exempting those under 21 who were already entitled to consume alcohol. In 2004 Australian PM John Howard, under political pressure, lowered govt. contributions to MPs superannuation from 15% to the standard 9%. However he exempted already serving MPs, allowing them to remain on the higher rate.