Maybe you only see the future pessimistically. I believe that if there was enough pressure in the UK, the US, China etc against the manufacture of arms then it would have a detrimental effect upon the supply of weaponry to conflict zones. How much of an effect would depend upon the government of the time, but they could be forced to pass legislation that hindered the trade in some way at least. The likelihood of that level of pressure being reached is undetermined and open to debate. It would also have to be sustained, as I suspect that the state's tactic would be small, grudging, and time-consuming measures. But I know one thing, the biggest problem any cause faces in gaining support is mobilising the masses that don't get involved because they don't really think it'll change anything.