Plaintiffs Joseph Celli and Fred Gentile are members of American Federation of Government Employees, AFL-CIO, Local 1592, employed at Hill Air Force Base, Utah. They appeal the district court's dismissal of their action against defendants, consisting of their national union, American Federation of Government Employees, AFL-CIO ("AFGE"), their local union, AFGE Local 1592 ("Local 1592"), and present and former union officials, including National President John N. Sturdivant, 13th District National Vice President Don Solano, National Representative Mike Hurley, Local 1592 President Jon Scott Blanch, and William Shoell and Harlan Francis. Their complaint included one federal claim based on title VII of the Civil Service Reform Act of 1978, 5 U.S.C. Secs. 7101-7135, its implementing Standards of Conduct regulations, 29 C.F.R. parts 457 and 458 (1993), and the Labor-Management Reporting and Disclosure Act of 1959, 29 U.S.C. Secs. 401-531. The complaint also included state law claims of breach of contract, negligence, intentional infliction of emotional distress, and defamation.

Defendants moved to dismiss under Fed.R.Civ.P. 12(b)(1) and 12(b)(6), or, in the alternative, for summary judgment under Rule 56. The district court dismissed the federal claim on grounds of failure to exhaust administrative remedies and lack of subject matter jurisdiction over suits against private parties under the Civil Service Reform Act.1 The court then dismissed the remaining claims for lack of pendent jurisdiction. We affirm on count one, the federal claim, but vacate as to counts two through five and remand for further consideration.

I. JURISDICTION UNDER LMRDA.

Messrs. Celli and Gentile pled their federal claim under the Labor-Management Reporting and Disclosure Act ("LMRDA"), 29 U.S.C. Secs. 401-531, as well as under title VII of the Civil Service Reform Act ("CSRA"), 5 U.S.C. Secs. 7101-7135, R. Vol. I, doc. 1, pp 1, 3, 12. They alleged jurisdiction pursuant to 29 U.S.C. Sec. 412, which allows any person to bring a civil suit in district court for violations of 29 U.S.C. Sec. 411, LMRDA's "bill of rights" for labor organization members. R. Vol. I, doc. 1, at p 3.

To sue a union in district court under LMRDA, a plaintiff must allege that the union qualifies under that statute's definition of "labor organization." That definition requires, inter alia, that the organization exist "for the purpose, in whole or in part, of dealing with employers concerning grievances, labor disputes, wages, rates of pay, hours, or other terms or conditions of employment." 29 U.S.C. Sec. 402(i). "Employer," however, is defined specifically to exclude "the United States or any corporation wholly owned by the Government of the United States or any State or political subdivision thereof." 29 U.S.C. Sec. 402(e). The Department of Labor and several courts have stated that LMRDA does not cover unions that represent only government workers, but it does cover those that represent only private sector workers and also so-called "mixed unions," i.e., those that deal with both public and private employers on behalf of their members concerning terms and conditions of employment.2

Fatal to jurisdiction under LMRDA in this case, however, is the failure of Messrs. Gentile and Celli to allege that either AFGE or Local 1592 is a LMRDA labor organization, i.e., a mixed union. Federal courts are courts of limited jurisdiction, and the presumption is that they lack jurisdiction unless and until a plaintiff pleads sufficient facts to establish it. United States v. Bustillos, 31 F.3d 931, 933 (10th Cir.1994); United States ex rel. Precision Co. v. Koch Indus., 971 F.2d 548, 551 (10th Cir.1992), cert. denied, --- U.S. ----, 113 S. Ct. 1364, 122 L. Ed. 2d 742 (1993); Penteco Corp. Ltd. Partnership-1985A v. Union Gas Sys., Inc., 929 F.2d 1519, 1521 (10th Cir.1991). Mere conclusory allegations of jurisdiction are not enough; the party pleading jurisdiction "must allege in his pleading the facts essential to show jurisdiction." Penteco, 929 F.2d at 1521 (quoting McNutt v. General Motors Acceptance Corp., 298 U.S. 178, 189, 56 S. Ct. 780, 785, 80 L. Ed. 1135 (1936)).3 If jurisdiction is challenged, the burden is on the party claiming jurisdiction to show it by a preponderance of the evidence. Bustillos, 31 F.3d at 933. Plaintiffs' failure to do so prevented the district court from hearing their LMRDA claim, and the court properly held that it lacked jurisdiction. Although plaintiffs' appeal is filed pro se, their original complaint was drafted by counsel and therefore is not entitled to the liberal construction we accord pro se pleadings.

II. NO DIRECT RIGHT OF ACTION AGAINST UNIONS UNDER 5 U.S.C. Sec. 7120.

The plaintiffs argue that because section 7120 of CSRA and section 411 of LMRDA both establish a bill of rights for union members and LMRDA section 412 explicitly allows direct suit against unions in district court, the same right of action is available under--or at least not precluded by--section 7120 of CSRA. For the reasons discussed above, no LMRDA right of action is available to these plaintiffs. And CSRA clearly states that complaints under section 7120 "shall be filed with the Assistant Secretary." 5 U.S.C. Sec. 7120(d). Neither the statute nor its implementing regulations at 29 C.F.R. parts 457 and 458 create a right of action in district court. See Martinez, 980 F.2d at 1041, n. 1; Local 1219, Am. Fed'n of Gov't Employees v. Donovan, 683 F.2d 511, 515 & n. 13 (D.C.Cir.1982); Parker v. Main, 804 F. Supp. 284, 287 (M.D.Ala.1992); Laity, 766 F. Supp. at 102. Although addressed to a separate section of CSRA, the Supreme Court's reasoning in Karahalios v. National Fed'n of Fed. Employees, Local 1263, 489 U.S. 527, 109 S. Ct. 1282, 103 L. Ed. 2d 539 (1989), regarding a right of action against a union for the violation of the duty of fair representation is instructive here: "Had Congress intended the courts to enforce a federal employees union's duty of fair representation, we would expect to find some evidence of that intent in the statute or its legislative history. We find none." Id. at 536, 109 S.Ct. at 1288. Messrs. Celli and Gentile have no direct cause of action against the defendants under section 7120 of CSRA.

The district court dismissed for lack of pendent jurisdiction the four counts that it deemed to be state law claims. It did not address the potential alternative basis for jurisdiction that arises from the fact that at least some of the incidents complained of appear to have taken place within a federal enclave.

Although a plaintiff must allege essential jurisdictional facts in a complaint, federal jurisdiction may be sustained on the basis of a statute not relied on or alleged in the pleadings. May v. Colorado Supreme Court, 508 F.2d 136, 137 (10th Cir.1974), cert. denied, 422 U.S. 1008, 95 S. Ct. 2631, 45 L. Ed. 2d 671 (1975). Here, it appears from the complaint that one or more of the events in question occurred at Hill Air Force Base, see, e.g., R. Vol. I, doc. 1, Ex. A at 7, 8, 15, which presumably qualifies, at least in part, as a federal enclave, thus affecting the question of federal court jurisdiction.

Whether federal enclave jurisdiction, a form of federal question jurisdiction, exists is a complex question, resting on such factors as whether the federal government exercises exclusive, concurrent or proprietarial jurisdiction over the property, when the property became a federal enclave and what the state law was at that time, whether that law is consistent with federal policy, and whether it has been altered by national legislation. See, e.g., Willis v. Craig, 555 F.2d 724, 726 (9th Cir.1977) (remanding for district court to make a finding on whether federal enclave jurisdiction exists); Lord v. Local Union No. 2088, Int'l Bhd. of Elec. Workers, AFL-CIO, 646 F.2d 1057, 1059-60 (5th Cir.1981), cert. denied, 458 U.S. 1106, 102 S. Ct. 3483, 73 L. Ed. 2d 1366 (1982); Macomber v. Bose, 401 F.2d 545, 546 (9th Cir.1968); Stokes, 265 F.2d at 665; Mater v. Holley, 200 F.2d 123, 124-25 (5th Cir.1952); Akin v. Big Three Indus., Inc., 851 F. Supp. 819, 821-22 (E.D.Tex.1994); Parker, 804 F. Supp. at 286; see also James Stewart & Co. v. Sadrakula, 309 U.S. 94, 99-100, 60 S. Ct. 431, 433-34, 84 L. Ed. 596 (1940); Chicago, R.I. & P. Ry. Co. v. McGlinn, 114 U.S. 542, 546-47, 5 S. Ct. 1005, 1006-07, 29 L. Ed. 270 (1885).

We express no opinion on whether federal enclave jurisdiction exists over the "state law claims" or whether "state law" is even applicable to any enclave involved. If the district court should decide that it does and that consideration of the preemption issue is appropriate, the court is also asked to examine whether the inclusion of 29 C.F.R. Sec. 458.2(a)(5)(c)5 within the "bill of rights" section of the Standards of Conduct regulations under title VII of CSRA precludes a finding of preemption in this case.

For the reasons stated, we AFFIRM the district court's order and judgment as to count one, VACATE as to counts two through five, and REMAND for further proceedings consistent with this opinion.