Legal Definitions - retrospective law

A retrospective law (also known as a retroactive law) is a statute or regulation that changes the legal consequences of actions or events that occurred *before* the law was enacted. Instead of only applying to future conduct, a retrospective law "looks backward" in time, altering rights, obligations, or legal statuses based on past circumstances.

• Example 1: New Tax Law

  Imagine a state legislature passes a new law in January 2024 that increases the tax rate on certain investment income. The law specifies that this new, higher rate applies to all investment income earned during the *entire 2023 tax year*. This means individuals and businesses must calculate their 2023 taxes using the new, higher rate, even though the law was not in effect for most of that year.

  Explanation: This is a retrospective law because it applies the new tax rate to financial transactions (earning investment income) that took place throughout 2023, which was *before* the law itself was officially enacted in January 2024. The legal obligation (the amount of tax owed) for past conduct is changed by a future law.

• Example 2: Building Safety Standards

  A city council enacts a new ordinance in March 2025 requiring all commercial buildings above a certain height to install advanced sprinkler systems. The ordinance includes a clause stating that any building constructed *before* January 1, 2010, must comply with this new requirement within two years, even though those buildings met all fire safety codes at the time of their original construction.

  Explanation: This ordinance is retrospective because it imposes a new obligation (installing advanced sprinkler systems) on buildings based on their past construction date. The legal standard for these older buildings is changed for events (their construction) that occurred long before the new law was passed.

• Example 3: Professional Licensing Requirements

  A professional licensing board for architects passes a new rule in June 2023 requiring all licensed architects to complete an additional 10 hours of continuing education in sustainable design every two years. The rule states that this new requirement applies to all architects whose licenses were *issued prior to* June 2023, even if they had already met the previous continuing education requirements for their current licensing period.

  Explanation: This rule is retrospective because it imposes a new ongoing obligation (additional continuing education) on individuals based on their past act of obtaining a license. The terms under which their existing licenses were granted are altered by a subsequent regulation.