What makes a requirement binding here
None of its own, and that is the defining fact about it. The Codex Alimentarius is the joint FAO/WHO food standards programme; its texts are recommendations to member governments, not law in any market. The cornerstone text is CXC 1-1969, General Principles of Food Hygiene, maintained by the Codex Committee on Food Hygiene and last modified in 2022 — the document that carries the HACCP framework most national food-safety regimes are built on.
By national adoption, and only then. A Codex code of practice acquires force when a member government takes it into its own law or references it in a standard, which means the same CXC number can be mandatory in one market, referenced as guidance in a second, and absent from a third. The WTO SPS Agreement gives Codex texts a further, indirect weight: a national measure aligned with Codex is presumed consistent with that agreement, which is why regulators reach for them even where they have not adopted them verbatim.