My understanding conforms with what Brian said. A couple of years ago a restaurant in Glen Ellen refused to let us to BYOB our previously opened bottle, telling us that it was against ABC regs. Not true. I’m not aware of any legal authority (such as case law or administrative interpretation), and it won’t be in the regs since regs usually just tell you what’s prohibited, not what’s permitted. I’ll see if I can find anything if I get a moment.
Brian’s solution to the problem is perfect.