There may indeed be laws, regulations or rules regarding back country waste disposal, depending on the park and the circumstances.
You're right! In the Yukon, NWT, and in Alaska there are already large areas that hunters, hikers and canoists MUST carry out ALL of their personal refuse [AKA night dirt] for disposal at regulated sites. This will become more and more common, in other wilderness access parks, as overuse of park interior camping and the need to conserve what we have continues to grow. Disregarding proper dumping proceedures is both dangerous to health and stupid, and ignoring the rules doesn't make it right.
We pick up after our pets, right? So what's different?