Go to http://www.vcdl.org.
Hunt up the link to official letters. There are a couple on there where the AG or the boss of Alcoholic Beverage Control board have written that OC is not prohibited.
Otherwise there is no law authorizing it. Its the absence of a law against it that makes legal.
The only law reference I've ever seen is that Article I, Section XIII of the VA Constitution confirms your pre-existing right to keep and bear arms.