Setting Enabled=False in a BocEnumValue with CotrolType Listbox does not render a disabled attribute, making it not really disabled. Because of that, it fails WCAG 1.4.3 "Color Contrast".
Accessibility test that found this: AccessibilityBocEnumValueTest.ListBoxDisabled
Note: It is possible that this broke when switching from .NET 3.5 to .NET 4.5.
ListControl.cs apparently does not do SupportsDisabledAttribute. Either this is invalid HTML and thus correct or a bug.