The Fourth Amendment generally requires police to knock and announce before entering, as the Supreme Court confirmed in Wilson v. Arkansas (1995). Courts allow exceptions when announcing would be dangerous or let evidence be destroyed. The War on Drugs made these raids routine, often carried out by SWAT teams.
In March 2020, Louisville police serving a no-knock warrant shot and killed Breonna Taylor, a Black emergency medical technician, in her apartment. The raid was part of a drug investigation focused on her former boyfriend, and no drugs were found. Her killing became a center of the 2020 protests.
Louisville banned no-knock warrants that June with an ordinance called Breonna's Law. Virginia passed a statewide ban in 2020, and Florida, Oregon and Connecticut have also barred them. Most states still allow them, and federal agents can still seek them, though the Justice Department limited their use in 2021.