This article is in today's National Post. It refers to the Canadian Navy forbidding its veterans from wearing their uniforms in public, including at memorial events, without permission. Nowhere does it mention re-enactors or vehicle crews (whether veterans or not) but it seem logical that they would have even more restrictions if this stands.
http://news.nationalpost.com/2013/06...thout-consent/
The practice in Canada at least has been that, if tastefully done, wearing of period uniforms is OK (medals not so much) especially given that once obsolete they are not officially "the Queen's uniform". Heck, they sell them in army surplus stores and have to assume they are being bought to be worn. Yet in this article it includes WW2 Navy vets.
Can of worms.