Noerr–Pennington doctrine

[3] In Noerr, the Court held that "no violation of the [Sherman] Act can be predicated upon mere attempts to influence the passage or enforcement of laws".

Similarly, the Court wrote in Pennington that "[j]oint efforts to influence public officials do not violate the antitrust laws even though intended to eliminate competition."

[15] The Ninth Circuit recently held that Noerr–Pennington also protects against RICO Act claims when a defendant has sent thousands of demand letters threatening suit.

First, such suits must be "objectively baseless in the sense that no reasonable litigant could realistically expect success on the merits.

"[18] If that threshold is met, the court will inquire whether the suit demonstrates evidence of a subjective intent to use governmental process to interfere with a competitor's business.

For example, in California Motor Transport v. Trucking Unlimited,[3] the United States Supreme Court held that the Noerr–Pennington doctrine did not apply where defendants had sought to intervene in licensing proceedings for competitors, because the intervention was not based on a good-faith effort to enforce the law, but was solely for the purpose of harassing those competitors and driving up their costs of doing business.

In 1993, the Supreme Court rejected a purely subjective definition of a "sham" lawsuit, and set out a two-part test.