Anyone able to answer this for Dan... I thought that as long as it was able to conform to registration requirements (headlight, indicators etc), and is registered for road use, then you're fine... I could be wrong though...
Lots of dirt bikes can be registered here but they must have a compliance plate & have been built to have been registered.
Even so unless you spend pretty big dollars on a dirt bike it won't like the long distance touring.
Go a road bike and let it deal with the dirt if required !