DVD Package/Design Standards?

[Natobasso]

I am normally a great searcher on the internet. I can find anything—even my wife! But I can't find any design standards for DVD Packaging as far as what images you can and cannot place on the cover. I've heard about a "only one gun" rule but can't verify it.

Anyone have some insight on this for the US DVD market? Any help or reference websites would be appreciated.