Use by Law Enforcement . Federal and International Law: While tear gas is classified as a chemical weapon and banned for use in international warfare under the Chemical Weapons Convention, the same treaty explicitly allows its use by law enforcement for "domestic riot control purposes". . Domestic Regulations: There are no specific federal laws in the U.S. that broadly regulate the use of tear gas by local law enforcement, which means rules and restrictions vary across different states and cities. . Local Restrictions: In the wake of protests, some cities and states (e.g., Portland, Denver, Seattle, and Washington state) have passed laws or court orders that either temporarily suspend or restrict the use of tear gas for crowd control, often requiring specific authorization and the exhaustion of other alternatives. . Conditions for Use: When law enforcement does use tear gas, they are often expected to give clear warnings and provide a safe path of egress for people to leave the area, though these guidelines are not always consistently followed or enforced.