WCAG is an interesting standard as its very difficult to meet and its difficult to automate tests. Often its important to use critical thinking, and have a solid argument for a position. Your case is a prime example of that.
If I had white text on a white background, with a clear, black outline on the text common sense suggests you would pass. If you are able to render the text clearly with an outline that is contrasted to either the text or the background you'd be able to make a case for passing this test. However, the only viable solution is a much darker outline (you can't go lighter than the white text) which may be visually clashing, so take precaution.
Also, I'd argue that the shadow would need to be clear to ensure that the text is still readable. I'd strongly recommend taking part of this question to User Experience.SE to get their opinion on a white text on an orange background, as they may be able to offer a more redable alternative that keeps with your branding.