The common law—as interpreted by United States courts in the light of reason and experience—governs a claim of privilege unless any of the following provides otherwise:
• the United States Constitution;
• a federal statute; or
• rules prescribed by the Supreme Court.
But in a civil case, state law governs privilege regarding a claim or defense for which state law supplies the rule of decision.
[Pub. L. 93–595, § 1], Jan. 2, 1975, [88 Stat. 1933]; amended Apr. 26, 2011, eff. Dec. 1, 2011.)