Swift & Courtney & Beecher Co. v. United States, 111 U.S. 22 (1884)

'The parties were not on equal terms. The appellant had no choice. The only alternative was to submit to an illegal exaction, or discontinue its business. It was in the power of the officers of the law, and could only do as they required. Money paid or other value parted with, under such pressure, has never been regarded as a voluntary act within the meaning of the maxim, volenti non fit injuria' (at 28-29).