A grandfather clause (or grandfather policy or grandfathering) is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from the new rule are said to have grandfather rights or acquired rights, or to have been grandfathered in. Frequently, the exemption is limited; it may extend for a set time, or it may be lost under certain circumstances. For example, a grandfathered power plant might be exempt from new, more restrictive pollution laws, but the exception may be revoked and the new rules would apply if the plant were expanded. Often, such a provision is used as a compromise or out of practicality, to allow new rules to be enacted without upsetting a well-established logistical or political situation. This extends the idea of a rule not being retroactively applied.
List of examples
Technology Tablet computers (and similar devices) with screen sizes below eight inches which ran Windows Phone 8 or Windows Phone 8.1 featured a traditional Windows desktop with legacy app support, alongside the ability to run the newer Metro-style apps. However, newer devices with sub-8-inch screens that ran the successor Windows 10 Mobile operating system had no legacy app capability, and, as such, could only run apps downloaded from the Windows Store. Most (if not all) owners of the older Windows 8 devices of that screen size class who upgrade to Windows 10 can still retain the old-style desktop and legacy app support, despite this upgrade. The Windows operating system has had several exceptions in the past. When extended support for Windows 7 ended on January 14, 2020, anyone using the OS no longer got security updates and were encouraged to upgrade to a newer OS or PC. However, Microsoft allowed companies and businesses that had the Professional and Enterprise volume licensed editions of Windows 7 to pay for additional support to give them time to migrate to newer operating systems like Windows 8.1 or Windows 10. Paid support for Windows 7 ended on January 10, 2023. When support for Windows 10 version 1703 ended on October 9, 2018, anyone using Windows 10 1703 no longer got security updates and were encouraged to upgrade to a newer version of Windows 10, such as version 1809. However, Microsoft allowed Surface Hub devices (which were no longer supported on newer versions of Windows 10) to still receive security updates for a longer period of time. Surface Hub devices running Windows 10 1703 are unsupported as of March 9, 2021. When support for Windows 10 version 22H2 ended on October 14, 2025, anyone using Windows 10 no longer got security updates and were encouraged to upgrade to a newer version of Windows 11. However, Microsoft allowed devices subscribed to the Extended Security Update (ESU) service to still receive security updates for one year, extending security support until October 13, 2026.
Science Some parts of bacterial taxonomy are legacied in a problematic state due to prevailing use in medical and industrial communities. A more proper name accepted by the microbiologist might not be used at all.
Law Many jurisdictions prohibit ex post facto laws, and grandfather clauses can be used to prevent a law from having retroactive effects. For example: In the UK, the offence of indecent assault is still charged in respect of crimes committed before the offence was abolished and replaced with sexual assault (among others) by the Sexual Offences Act 2003. Many acts requiring registration to practice a particular profession incorporated transition or "grandfather sections" allowing those who had already practised for a specified time (often three or four years) to be registered under the act even if they did not have the training or qualifications required for new applications for registration. Examples are the Nurses Registration Act 1901 in New Zealand and the Nurses Registration Act 1919 in England and Wales.
Canada In 1965, the Canadian government under Prime Minister Lester B. Pearson passed legislation that required senators to retire when they reached the age of 75. However, senators appointed before the legislation was passed were exempted from the mandatory retirement rule. When Quebec enacted the Charter of the French Language in 1977, making French the province's official language, the famous Montreal kosher-style deli Schwartz's was allowed to keep its name with the apostrophe, a feature not used in French in the possessive form. During Canada's federal Redistribution, a grandfather clause ensures that no province can have fewer seats after Redistribution than it did in 1985.
Macau In 2012, Macau increased the permitted age of entering casinos to 21. However, casino employees between the ages of 18 and 21 before the change were still permitted to enter their places of employment. This category was exhausted by the end of 2015.
United States Section 1 of Article Two of the United States Constitution requires that the President be a natural born citizen of the United States. However, at the beginning there had to be another category of persons eligible for that office: those who were citizens of the United States at the time of the adoption of the Constitution. Without that provision, it would have required a strained reading to construe that all Presidents born in the colonial era were born in the United States, which did not exist prior to the adoption of the United States Declaration of Independence on July 4, 1776. In 1949, standards were passed requiring certain fire safety improvements in schools. However, older schools, such as the Our Lady of the Angels School in Illinois, were not required to be retrofitted to meet the requirements, leading to the deadly Our Lady of the Angels School fire in which 92 students and three teachers died. in 1951, the Twenty-second Amendment to the United States Constitution was passed and made it so that Presidents are only allowed to be elected to two terms; other sections include that a President shall only be elected to one term if their first term is less than two years past the day scheduled Inaugurations take place. It didn't apply to the then-president Harry S. Truman but he ended up dropping out of the 1952 race after winning his only full term in 1948. In the 1980s, as states in the US were increasing the permitted age of drinking to 21 years, many people who were under 21 but of legal drinking age before the change were still permitted to purchase and drink alcoholic beverages. Similar conditions applied when New Jersey and certain counties in New York raised tobacco purchase ages from 18 to 19 years in the early 2000s. In 1984, Mississippi passed a law changing its official mode of capital punishment from the gas chamber to lethal injection. Under the new law, anyone sentenced after July 1, 1984, was to be executed by lethal injection; those condemned before that date were "grandfathered" into the gas chamber. Therefore, three more convicted murderers would die in the chamber—Edward Earl Johnson and Connie Ray Evans in 1987, and Leo Edwards in 1989. In 1998, the Mississippi Legislature changed the execution law to allow all death row inmates to be executed by lethal injection. During the Federal Assault Weapons Ban publicized on August 25, 1994, certain firearms made before the ban's enactment were legal to own. Automatic weapons that were manufactured and registered before the Firearm Owners Protection Act (enacted May 19, 1986) may legally be transferred to civilians. California governor Jerry Brown, who served as the state's governor from 1975 to 1983, was able to run for the governorship once more in 2010 due to a grandfather clause in the state constitution that went to effect in 1990. In 2013, Tennessee enacted a law requiring that products labeled as "Tennessee whiskey" be produced in the state, meet the legal definition of bourbon whiskey, and also use the Lincoln County Process. The law specifically allowed Benjamin Prichard's Tennessee Whiskey, which does not use the Lincoln County Process, to continue to be labeled as such. In March 2026 the Federal Communications Commission issued an order banning the sale of new foreign-made wifi routers and models made after the order unless a company has an exemption to do from the Pentagon or the Department of Homeland Security on national security grounds. However the order did not effect previously purchased routers or prevent the continued sale, import, or marketing of router models that were previously approved through the FCC’s equipment authorization process.
Standards compliance Strict building codes to withstand frequent seismic activity were implemented in Japan in 1981. These codes applied only to new buildings, and existing buildings were not required to upgrade to meet the codes. One result of this was that during the great Kobe earthquake in 1995, many of the pre-1981 buildings were destroyed or written off, whereas most buildings built post-1981, in accordance with the new building codes, withstood the earthquake without structural damage. Construction codes also require newly-erected buildings to be certain distances from roads, shorelines, bodies of water, etc. Already-present structures that existed prior to the laws' going into effect are often exempt, especially private homes. Moderate degrees of upkeep, repairs, and renovations to such dwellings may also be permitted, but such alterations may be limited to less than a percentage of the total building structure; if more than that amount of the building must be replaced, the owners may be required to have it relocated to a code-compliant locale. Upgrades in building-construction, safety, utilities, etc. may be required of the rebuilt home, as well. Wigwag-style railroad crossing signals were deemed inadequate in 1949 and new installations were banned in the United States. Existing wigwag signals were allowed to remain and 75 years later, there are still about 17 wigwag signals in use on railroads in the United States. The UK's national rail infrastructure management company Network Rail requires new locomotives and rolling stock to pass tests for electromagnetic compatibility (EMC) to ensure that they do not interfere with signalling equipment. Some old diesel locomotives, which have been in service for many years without causing such interference, are exempted from EMC tests and are said to have acquired grandfather rights. The Steel Electric-class ferryboats used by Washington State Ferries were in violation of several U.S. Coast Guard regulations, but because they were built in 1927, before the enactment of the regulations, they were allowed to sail. Those ferries were decommissioned in 2008. Tolled highways that existed before the Interstate Highway System are exempt from Interstate standards despite being designated as Interstate highways. Many such toll roads (particularly the Pennsylvania Turnpike) remain as such. However, tolled highways built since the Interstate system, such as the tolled section of PA Route 60 and PA Turnpike 576, must be built or upgraded to Interstate standards before receiving Interstate designation. Both highways are to be part of the Interstate system, with PA 60 now I-376 and PA Turnpike 576 to become I-576 in the near future. As well, U.S. Interstate Highway standards mandate a minimum 11-foot median; however, highways built before those standards have been grandfathered into the system. The Kansas Turnpike is the most notable example, as it has been retrofitted with a Jersey barrier along its entire 236-mile (380-km) length.