It the laws that determine use of force, as established in Graham v Connor. https://supreme.justia.com/cases/federal/us/490/386/#:~:text=Syllabus-,PetitionerGrahamadiabeticaskedhisfriendBerry,StatesConstitutionand42U.S.C. Edit: Sorry the law is actually the 8th ammendment to the constitution, this is the case that outlines it.