A grandfather clause is a provision in a law or contract that allows old rules to continue to apply in certain situations. The term originated in the U.S. during the late 19th century, when conservative lawmakers seeking to enact restrictive voting laws were forced to make exceptions for young people whose grandfathers had had full voting rights before the Civil War. This is the origin of the verb grandfather, which means to exempt from new rules or restrictions (a person or thing predating the new rules or restrictions). It is often followed by in.
The verb grandfather is still primarily an Americanism. Most of the few examples we find in non-U.S. sources are in reference to American things.
Though the word is rare, it is well established and should be familiar to most close followers of news and politics, especially in the U.S., so there is no need to put it in quotation marks.
Examples
Any changes would not affect existing businesses, which would be grandfathered in. [Denver Post]
hat sounds like a potential area for compromise; perhaps we should grandfather the burning of coal at existing plants, at least for a time. [Paris Post-Intelligencer]
Apart from sharply higher compensation demands, the union’s pre-lockout proposal also included a full grandfathering of all officials in the existing defined benefit plan. [ESPN]
But if Congress doesn’t change the law, or if it grandfathers Roth IRAs that already exist, you’ll have lost a great opportunity to reduce taxes. [Investing Daily]
‘We’re concerned with any other type of drive-in dealing with new construction,’ Mayor Ben Romeo told the North Jersey Record, ‘as opposed to the current drive-thrus, which are grandfathered into existence.’ [Daily Mail]