Liechtenstein

Each member shall notify the committee and publish its measures on the use of customs brokers.

In Switzerland there is no obligation to use a customs broker.
See Article 26 of the Customs Act
https://www.admin.ch/opc/fr/classified-compilation/20030370/index.html

In liaison with Article 75 of the Customs Ordinance
https://www.admin.ch/opc/fr/classified-compilation/20052713/index.html