Can a federal district court abstain from exercising jurisdiction in a matter of substantial public concern?

District courts have an obligation and a duty to decide cases properly before them, and "[a]bstention from the exercise of federal jurisdiction is the exception, not the rule." Colorado River Water Conservation Dist. v. United States, 424 U.S. 800, 813, 96 S.Ct. 1236, 47 L.Ed.2d 483 (1976). Nevertheless, Burford abstention allows a federal district court to abstain from exercising jurisdiction if the case presents "difficult questions of state law bearing on policy problems of substantial public import whose importance transcends the result in the case then at bar," or if decisions in a federal forum "would be disruptive of state efforts to establish a coherent policy with respect to a matter of substantial public concern." Colorado River, 424 U.S. at 814, 96 S.Ct. 1236; see also Burford v. Sun Oil Co., 319 U.S. 315, 63 S.Ct. 1098, 87 L.Ed. 1424 (1943).