This paper establishes an aspect of Bohr's correspondence principle, i.e. that quantum mechanics converges in the high frequency limit to classical mechanics, for commuting semiclassical unitary operators. We prove, under minimal assumptions, that the semiclassical limit of the convex hulls of the quantum spectrum of a collection of commuting semiclassical unitary operators converges to the convex hull of the classical spectrum of the principal symbols of the operators.

32 pages. Presentation substantially revised and reorganized for clarity. Main Theorem is now in in the introduction, and non central materialshave been moved to appendix 1 and appendix 2. Small mistake in the application of Cayley transform has been fixed