Is the 1925 Geneva Protocol a dead letter, if nobody is willing to enforce it?
Written during the time of the ill-fated League of Nations, the Protocol outlawed first use of chemical weapons, and is still being ratified in various places - Syria ratified it in 1968, Moldova in 2010. It was widely accepted as applying to use anywhere, including domestically, although some signatories weren't entirely happy to share that view.
The Protocol was written in a simpler time, when technology limitations meant that access to chemicals was restricted, the means of delivery were few, and pretty obvious, and the idea of using such weapons against your own citizens was almost unthinkable. Besides, they weren't very accurate, being vulnerable to wind shifts and the like.
The world is a much more complex place now, and delivery of chemical weapons much simpler, so the idea that only sovereign nations might use them is a flawed one. That has implications for enforcement, and I'm not convinced that existing international bodies are best suited to dealing with the new environment.
So, if it is to be assumed that last night's vote rules out British involvement in Syria in the near term, does this mean that we have effectively chosen not to enforce the Protocol?
I hope not. But perhaps if the United Kingdom finds itself in a position to bring the UN Security Council together to address the question of treaty enforcement in an era where sovereign states are not the only players, this may be an opportunity gained, rather than one lost.