27 CFR § 1.56 - Oaths and affirmations.
A document must be verified by an oath or affirmation taken before a person authorized by the laws of the United States or by State or local law to administer oaths or affirmations in the jurisdiction where the document is executed when required by:
(a) Regulation; or
(b) An appropriate TTB officer.
The following state regulations pages link to this page.