Is there an exception to the general rule that "an issue not presented to the trial court cannot be raised for the first time on appeal"?

Shorb's double jeopardy claim raises solely legal questions and is therefore not barred by the general rule that "an issue not presented to the trial court cannot be raised for the first time on appeal." United States v. Whitten, 706 F.2d 1000, 1012 (9th Cir. 1983) (recognizing exception to this rule "where the issue conceded or neglected below is purely one of law"), cert. denied, 465 U.S. 1100 (1984). Moreover, we have the benefit of the district court's opinion on the merits because Shorb filed a motion with the district court on Dec. 2, 1994, asking for release pending appeal. In denying Shorb's motion, the district court considered whether the double jeopardy claim raised a "substantial question of law or fact likely to result in (i) reversal, [or] (ii) an order for a new trial." 18 U.S.C. Sec. 3143(b)(1)(B). The district court held that it did not.