The Swiss Federal Nuclear Safety Inspectorate ENSI is the regulatory authority responsible for nuclear safety and the security of nuclear installations in Switzerland. Its work is based on various legal foundations, in particular the Nuclear Energy Act and the Radiation Protection Act.

ENSI issues guidelines in its capacity as the regulatory authority or based on a mandate in an ordinance. Guidelines are enforcement aids that convert legal requirements into concrete terms and facilitate uniform implementation. ENSI can order measures by means of decrees and approvals.