...the Washington Naval Conference! By limiting the tonnage and type of capital vessels on an individual nation-basis, all sorts of "cleverness" was incentivized...
Excellent example. After the horrificness that was WWI, there were all sort of attempts at wishful-thinking, "let's just make war illegal!" treaties and agreements. Some stuck (not even the Nazis used mustard gas), but must of the treaties turned out to be so much toilet paper. All the Washington Treaty accomplished, as Eddie points out, was to ensure the players had better weapons when the next war kicked off.
Bottom line is, the real problems WRT landmines and CBUs are caused by players who aren't subject to any of the treaties, or will simply ignore them. Countries that feel like they need them will continue to use them, and the rest will continue to make good money on selling them.
Besides, none of these treaties have any sort of practical enforcement element to them. What will we all do if a signatory country does use CBUs in the next war? "Hey! No fair! Cheater McCheterson!"