antitrust claims. The only potential impact on the state arising from federal adjudication of those claims is the limitation of the District to the state courts if it wishes to pursue those claims which are not precluded by state action immunity. That result does not affect in the slightest California’s ability to take acts necessary to regulate water and water rights, including measures aimed at precluding waste and unreasonable use. The district court thus correctly concluded that Burford abstention was inappropriate.
The District’s reliance upon Colorado River Water, which permits abstention on the grounds of “wise judicial administration,” is similarly misplaced. Colorado River Water involved claims over which there existed concurrent state and federal jurisdiction. But here, as in Turf Paradise, the federal courts have exclusive jurisdiction over federal antitrust claims. See 670 F.2d at 821. Thus, the exercise of federal jurisdiction does not result in any waste of judicial resources. “Wise judicial administration” does not call for abstention in such circumstances. See id. Colorado River Water is further inapposite given the reliance upon the McCarran Amendment in that case and the absence of any similar federal legislation counseling in favor of unified state proceedings in this case.
Abstention is an extraordinary and narrow exception which is appropriate only where the consequences of exercising federal jurisdiction outweigh our obligation to adjudicate suits over which we have jurisdiction. See Turf Paradise, 670 F.2d at 819 (citing Colorado River Water, 424 U.S. at 813, 96 S.Ct. at 1244). The federal courts are obliged to exercise their jurisdiction in all but the most exceptional cases. This is not such an exceptional case. There was no abuse of discretion.
Ill
In denying the City's motion for summary judgment, the district court held that the City was not entitled to state action immunity from the antitrust laws under the doctrine enunciated in Parker v. Brown, 317 U.S. 341, 63 S.Ct. 307, 87 L.Ed. 315 (1943). We review this decision de novo. See State of Idaho v. Hodel, 814 F.2d 1288, 1292 (9th Cir.1987) (citing Ashton v. Cory, 780 F.2d 816, 818 (9th Cir.1986)). We reverse the district court’s denial of summary judgment.
A
In Parker v. Brown, 317 U.S. 341, 63 S.Ct. 307, 87 L.Ed. 315 (1943), the Supreme Court held that no federal antitrust liability arises for an anti-competitive act by a state acting “as sovereign.” Cities are not themselves sovereign. City of Lafayette v. Louisiana Power & Light Co., 435 U.S. 389, 412, 98 S.Ct. 1123, 1136, 55 L.Ed.2d 364 (1978). Nevertheless, the state “as sovereign” may sanction anticompetitive municipal activities and thus shield its cities with Parker immunity for such activities. Id. at 413, 98 S.Ct. at 1137. Where a city claims Parker immunity, however, the court will require that the state policy authorizing the challenged restraint be clearly articulated and affirmatively expressed. See id. at 410, 98 S.Ct. at 1135. See also California Retail Liquor Dealers Ass’n. v. Midcal Aluminum, Inc., 445 U.S. 97, 105, 100 S.Ct. 937, 943, 63 L.Ed.2d 233 (1980); New Motor Vehicle Board of California v. Orrin W. Fox Co., 439 U.S. 96, 109, 99 S.Ct. 403, 411, 58 L.Ed.2d 361 (1978). A city need not point to a specific, detailed legislative authorization before it may properly assert a Parker defense to an antitrust suit. See Springs Ambulance Service v. City of Rancho Mirage, 745 F.2d 1270, 1273 (9th Cir.1984) (citing Lafayette, 435 U.S. at 415, 98 S.Ct. at 1138) (statute authorizing city to contract for ambulance services contemplated municipal provision of exclusive, free ambulance service). That is, not every anticompetitive effect of a statute need be articulated in order to satisfy the “clear articulation” requirement. See Preferred Communications, Inc. v. City of Los Angeles, 754 F.2d 1396, 1413-14 (9th Cir.1985). “No legislature can be expected to catalog all of the anticipated effects of a statute ...” Town of Hallie v. City of Eau Claire, 471 U.S. 34, 43, 105 S.Ct. 1713, 1719, 85 L.Ed.2d 24 (1985). So