My roommate and I were discussing what the US government should do about Syria, and he brought up political assassination. Maybe, he suggested, a few high-profile failures in the past had caused Western governments to unfairly neglect it as a viable foreign policy alternative.
His suggestion would no doubt elicit knee-jerk opposition from many -- myself included -- but the logic is hard to deny. Although the US government wants Assad to step down, it has precious little leverage over him, short of full-scale military invasion. As long as Assad remains convinced an attack is unlikely and infeasible, he can safely ignore the pronouncements of the US State Department. His calculus would have to change, however, if defying the US meant dodging a steady stream of assassination attempts.
It's an interesting thought. Eroding the international proscription against assassination would dramatically increase American leverage over small-time despots and geographically localized conflicts. Can anyone deny that the US would have more quickly achieved its ends in Libya if it had the option of simply blowing up Qaddafi? Either Qaddafi would have stepped down, knowing he had no other option, or he'd probably just be dead and gone. We certainly wouldn't have spent the last six months bombing the Libyan desert, in order to ensure that Libyan rebels survive long enough to do our dirty work for us.
(Some people, I'm sure, also have moral objections to state-directed killings. And fair enough. But when, as in Libya, the practical alternative might be a prolonged military conflict, assassination seems, if anything, the more humane option.)
If you carry the reasoning only this far, it does seem that the US would benefit from again pursuing political assassination as an extension of its foreign policy. And you might think that smaller nations would be generally opposed to a loosening of norms against assassination.
I think this reasoning has it backwards, however. It's somewhat counterintuitive, but proscriptions against assassination are actually most beneficial to large, rich nations like the US.
That's because hiring, training, and equipping a team of assassins is relatively cheap. So cheap, in fact, that most nations could probably do it. So while the spectre of the assassin's bullet might force Assad to take America's preferences more into account when making political decisions, it would also force Obama to take Syria's preferences more into account. He, like, Assad, would have to live with the constant fear that some miffed international opponent had sent a team of killers his way.
In a world where assassination was an acceptable foreign policy tool, all world leaders would gain more leverage over all other world leaders. But right now, Syrian leaders have exactly zero leverage over American leaders, while the United States, with enormous economic influence and unrivaled military power, has significant influence over Syria. So the benefit to Syria (a voice in US policymaking!) would be considerably larger than the benefit to the United States (marginal at best). In other words, international norms against assassination are helpful in maintaining the status quo. They increase the influence of large, rich, militarily powerful nations, at the expense of small, poor, militarily weak nations.
It's true that the threat of military force or economic sanctions are awkward foreign policy tools. They're ill-suited for a lot of the foreign policy problems the US faces -- Syria is just the latest example -- and there's often no middle option that would work better. But for American policymakers, the key feature of the use of military and economic force is not just their versatility, but their exclusivity. Few other nations have similar implements at their command. So American policymakers surely prefer to live in a world where other, less exclusive foreign policy options are foreclosed by law or custom.