Section 1338 of title 28 of the United States Code (section 1338) provides in relevant part: "The district courts shall have original jurisdiction of any civil action arising under any Act of Congress relating to patents . ... Such jurisdiction shall be exclusive of the courts of the states in patent ... cases." The United States Supreme Court in Christianson v. Colt Industries Operating Corp. (1988) 486 U.S. 800 (Christianson) set out a test to determine whether a case is subject to the exclusive jurisdiction described in section 1338. The court held that section 1338 jurisdiction extends "only to those cases in which a well-pleaded complaint establishes either that federal patent law creates the cause of action or that the plaintiff's right to relief necessarily depends on resolution of a substantial question of federal patent law, in that patent law is a necessary element of one of the well-pleaded claims." (Christianson, at p. 809; see also Franchise Tax Bd. v. Laborers Vacation Trust (1983) 463 U.S. 1, 13 "Even though state law creates appellant's causes of action, its case might still 'arise under' the laws of the United States if a well-pleaded complaint established that its right to relief under state law requires resolution of a substantial question of federal law in dispute between the parties.".) The court later restated the test (under the general jurisdictional statute for claims arising under the Constitution, laws, or treaties of the United States, 28 U.S.C. 1331) to address federalism concerns: "The question is, does a state-law claim necessarily raise a stated federal issue, actually disputed and substantial, which a federal forum may entertain without disturbing any congressionally approved balance of federal and state judicial responsibilities." (Grable & Sons Metal Products, Inc. v. Darue Engineering & Mfg. (2005) 545 U.S. 308, 314 (Grable).) In reaching this conclusion in each case, the court considered other instances in which it found a state law claim presented a substantial issue of patent law. For example, a state law claim for business disparagement, based upon the defendant's warning to the plaintiff's customers that the plaintiff's product infringed the defendant's patent, invoked section 1338 jurisdiction, because it required the plaintiff to prove that its product did not infringe. (Additive Controls & Measurement Sys. v. Flowdata (Fed.Cir. 1993) 986 F.2d 476, 478.) Section 1338 jurisdiction existed over state law claims for injurious falsehood and violation of Business and Professions Code section 17200, because the plaintiff's allegation that the defendant asserted ownership of patents that were invalid or unenforceable required the plaintiff to prove patent invalidity or unenforceability. (Hunter Douglas, Inc. v. Harmonic Design, Inc. (Fed.Cir. 1998) 153 F.3d 1318, 1329, overruled on other grounds in Midwest Industries, Inc. v. Karavan Trailers, Inc. (Fed.Cir. 1999) 175 F.3d 1356.) Section 1338 jurisdiction encompassed a state law breach of contract claim arising from a contractual duty to assign certain patents, because the plaintiff had to prove that the application for the patent at issue fell within the patent examining guidelines as a "continuation-in-part" of a prior application. (University of West Virginia v. Vanvoorhies (Fed.Cir. 2002) 278 F.3d 1288, 1295; see also Pro-Mold & Tool Co. v. Great Lakes Plastics (Fed.Cir. 1996) 75 F.3d 1568, 1574 determination of whether alleged inequitable conduct in prosecution of a patent application constitutes unfair competition is within exclusive jurisdiction of Federal Circuit.)