Roe v. Wade (1973) was a landmark decision of the U.S. Supreme Court in which the Court ruled that the Constitution of the United States protects a pregnant woman's liberty to choose to have an abortion without excessive government restriction.
Several states have enacted so-called trigger laws which would take effect in the event that Roe v. Wade is overturned, with the effect of outlawing abortions on the state level. Those states include Arkansas, Kentucky, Louisiana, Mississippi, North Dakota and South Dakota. Additionally, many states did not repeal pre-1973 statutes that criminalized abortion, and some of those statutes could again be in force if Roe were reversed.
Background info for non-US Tilderinos