A contract written in one country often cannot be used directly in another. The legal terms, the definitions, the assumptions about what counts as proof or consent, all of these are shaped by the jurisdiction where the document was created. Moving the document across a border does not move the legal context with it.
This is a problem that exists in paper systems. I think it becomes more interesting in digital ones.
$SIGN uses a schema registry where attestations follow structured templates. A schema defines what fields a credential contains and what those fields are meant to represent. Any institution can register one.
But a schema written in a jurisdiction where identity means a government issued biometric record carries different assumptions than one written where identity means a community attestation or a tax number. The field names might be identical. The meaning of what goes inside them is not.
Sign Protocol can standardize the format. Whether it can standardize the meaning behind the format is one question. Whether a verifier in a different jurisdiction will recognize the issuer as trustworthy under their local law is a second question that sits entirely outside the protocol.