The Sherman Antitrust Act was a landmark piece of federal legislation passed in 1890 and "intended to prevent all contracts, combinations, and conspiracies which restrain or monopolize trade.

In two cases interpreting these laws (Eastern Railroad Conference v. Noerr Motor Freight Inc.[3] and United Mine Workers v. Pennington[4]), the Supreme Court had created the Noerr–Pennington doctrine.

Trucking Unlimited was the named plaintiff for a group of fourteen companies that accused the California Motor Transport Co. and eighteen others of forming a joint war chest.

The appeals court considered that the Noerr and Pennington cases did not apply to "...a conspiracy to unreasonably restrain or monopolize trade through the use of judicial and administrative adjudicative proceedings.

In Noerr, the Court had said in passing that this right would not protect companies when the lobbying actions were "a mere sham" to conceal activities intended to directly interfere with competitors.

Douglas went on to distinguish between influencing public officials, which was allowed, and denying competitors access to government decision-makers and usurping regulatory processes for commercial ends.