Try to use primary law online that is official and authenticated, if available.
Official Legal Resource = One that has been governmentally mandated or approved by statute or rule.
If there is a conflict between an official source (eg. official United States Code) and an unofficial source (U.S. Code Annotated or United States Code Service), the official source prevails.
Authentic Legal Resource = Content has been verified by a government entity to be complete and unaltered. Technologies are in place to prevent tampering with the text, such as encryption or watermarking. (For a more complete definition, see American Association of Law Libraries (AALL) State-by-State Report on Authentication of Online Legal Resources.)
Bluebook Rule Bluebook Rule 18.2.1, concerning Internet citation, states that the Bluebook prefers citing the authenticated source, and if none is available, the official source.