There are multiple definitions - click on the translation that matches your context.

Unterschriftsberechtigung

Substantiv

partial

signatory

noun

Comparative law notes

Germany

This is the term describing the person who have signing authority, not the authority itself.

Definitions of signatory

English

a person or legal entity that signs and is bound by a document (=must act in accordance with its terms), often used to describe governments that sign a treaty, convention or similar document

The United States is not a signatory to that treaty, and thus is not bound to follow any of its provisions.