I didn't make the law, but technically, what you describe is not lawful. I think, technically, you can do it... but vendors can't distribute the compiled code that does it without a license from the DVD consortium folks.
It depends on the type of DVD you use. If for instance it's a movie DVD using something like CSS (remember DVD Jon?) and you access it's content by breaking the CSS "protection" then you're right. Basically if you need specific codecs or circumvent certain "protection" layers it would probably be something that you might want to check with a legal expert. In any other case where you want to access a plain DVD, AFAIK this is completely legal anywhere in the world.
