What makes a requirement binding here
None of its own. VICH — International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products — was formed in April 1996, triggered by the OIE, now the World Organisation for Animal Health, and holding its first Steering Committee meeting in Paris that month. It is a programme of collaboration between the regulatory authorities and animal-health industries of three regions: the European Union, Japan and the United States. Canada and Australia/New Zealand hold observer status. It publishes guidelines and enacts nothing.
By regional implementation, exactly as ICH’s do. In the United States, FDA’s Center for Veterinary Medicine issues VICH guidelines as Guidance for Industry documents — VICH GL9 as GFI #85, VICH GL6 as GFI #89 — and the guidance is what a sponsor works to. The European Union implements them through its veterinary framework, and Japan through its own authority. The goal is narrow and clearly stated: harmonising the technical data requirements the three participating authorities apply before granting a marketing authorisation.