Richard Price is a political scientist at the University of British Columbia and author of "The Chemical Weapons Taboo." We spoke this afternoon about the history of the prohibition on chemical weapons, past efforts to punish violations and whether the norm will fall apart if the United States doesn't strike Syria. The transcript has been edited for clarity and length.

Hussein Malla/AP
Hussein Malla/AP

Ezra Klein: Let’s start with the most basic question. How do you define a “chemical weapon”?

Richard Price: That’s actually a really interesting question with a lot of controversy behind it. They were originally defined back in 1899 as shells that spread asphyxiating or debilitating gases. The chemical weapons convention served to both broaden and tighten that definition. It included tear gases to be prohibited as a method of warfare. So there’s a big controversy that peaked after the United States used tear gas in Vietnam, where we argued it shouldn’t be prohibited. But the idea is, if you’re in the battlefield you’re not going to sit around testing what kind of gas it is. If people misperceive it, it can invite immediate and more fatal retaliatory attacks. So you actually have tighter restrictions in international war than you do in domestic policing, where tear gas is often used.

EK: And is the idea that chemical weapons are more lethal than conventional weaponry? Because the history of warfare is thick with examples of humans being pretty good at killing each other with, say, incendiary devices.

RP: The primary idea is that they are indiscriminate and an inherent threat to civilian populations. The kernel of that really arose in the aftermath of World War I. Chemical weapons were used on a wide scale in that conflict. There was a real fear, particularly as air technology got better, that there’d be massive chemical attacks on cities. They were really the first weapon of mass destruction but they’ve never quite lived up to that destructive capacity. Nuclear and biological weapons today have much more massive destructive capacity.

EK: But are they that much more indiscriminate? It seems that incendiary weapons could set uncontrollable fires that spread from town to town, particularly in the early 20th century when cities were a lot less fireproof than they are today, while with chemical weapons you can know with reasonable certainty how far they’ll go.

RP: That indiscriminate nature is one part of the story, but there are several other key parts. One is that the weapon was banned before people had them around. In 1899 there was a Hague peace conference that produced a declaration banning the use of asphyxiating shells even though nobody had them yet. So nobody was giving up a valuable weapon in their arsenal yet. That didn’t prove to be a consequential restraint in the short term, as World War I exploded it. But the Geneva Protocol was facilitated in 1925 because they didn’t feel they were doing anything new. They had already banned chemical weapons, even if the ban wasn’t very effective.

It then came to have much more significance because of what I call moral entrepreneurs. People who believe in a norm in places of institutionalized decision-making power. You get somebody like President Roosevelt, in World War II, who had a personal antipathy to the use of gas and declares the U.S. won’t be the first to use the weapon. And you really don’t see chemical weapons used against soldiers or cities in World War II. So you get this tradition of non-use, and there’s also this political dynamic where no one wants to cross the line even Hitler didn’t cross. He did use gas in the concentration camps, but not really on the battlefield. So in war there becomes this idea that they must be really bad if even Hitler wouldn’t use them.

EK: What have been the major uses of chemical weapons since 1925?

RP: One reason why non-use in World War II was so surprising was that on the eve of the war Italians used them in Ethiopia. So it looked like World War II would be like World War I, with lots of chemical weapons. But they largely went unused in the actual war. Egypt used them in the 1960s against Yemen. The last major use was by Iraq in its war against Iran, and then Iraq used them against their own Kurdish population in 1988. So the Syrian use appears to be the first major use in 25 years. That’s a pretty good track record for a norm of war.

EK: Presumably the reason we care about a norm of war like that is that we believe it will save lives. Is there good reason to believe the norm against chemical weapons has saved lives, or has it just meant deaths through conventional weaponry?

RP: Skeptics say countries figure out ways to do what they want to do. The United States in 2013, for instance, doesn’t need chemical weapons. It has other ways to accomplish its military ends. There are two responses. One is that these weapons can have indiscriminate effects. Presuming the Assad regime used this weapon, it was because they didn’t accomplish their goals with conventional weapons alone. Conventional weapons in cooperation with chemical rounds can have a much bigger effect if you’re trying to target a large area. So perhaps people have been spared, compared to a world without a taboo in which this is a regular part of war.

Second, there’s a really interesting way in which chemical weapons have helped contribute to a larger effort to constrain war. In the 1980s there was an effort to ban anti-personnel land mines. I was at a lot of those diplomatic conferences. I was really struck by how many times diplomats from various countries made the argument that we’ve already banned one weapon and so we can do this. That precedent made it seem a lot more possible. I’m really convinced that if there wasn’t a quite successful track record on restraining chemical weapons, many more countries around the world would think it preposterous that you could ban a weapon that’s used as widely as land mines. So I think there are some spillover benefits.

EK: Is there a past history of violations of the norm being punished by outside actors? You mentioned, for instance, Iraq in the Iran-Iraq war, but I don’t remember them getting shelled by the United States for their actions.

RP: There’s not much of a history of legal enforcement in instances like this. After the Iran-Iraq war, there was no response. All the U.N. could muster was a weakly worded condemnation of chemical weapons that didn’t name names. And the U.S. was in no rush to see Iraq punished, as they didn’t want to see Iran win.

But there were the U.N. resolutions to disarm Iraq, and the U.S. did attack Iraq in 1998 to try and degrade some of the weapons-of-mass-destruction capability because the inspectors were ordered out. An argument could be made that that was a kind of enforcement. But there was no Security Council authorization and there was a much larger set of targets, so it wasn’t just about disarmament.

EK: Do you think striking Syria is necessary to uphold the norms against chemical weapons?

RP: I’m a bit skeptical. This immense explosion of outrage and horror around this episode wouldn’t leave a future user of chemical weapons thinking they could just go ahead. It’s a very high-cost thing with a very real risk. And it’s not as if there are 40 states out there waiting to use these weapons. Only seven or eight states haven’t joined the convention, including Syria, North Korea and Egypt.

EK: So that makes it sound like there’s no reason to hit Syria.

RP: I would word it this way: Bombing Syria would be the strongest possible upholding and reinforcement of the norm. Will the norm fall by the wayside if that doesn’t happen? No, I don’t think it will. But if there was a strike to enforce it, that would be a watershed moment in many respects. Norms regarding warfare have often been quite effective, like the treatment of prisoners of war. They’re sometimes violated, of course, but a lot of them are treated with a minimal level of decency. These norms trudge on, despite violations, because of beliefs about reciprocity and decency. One violation does not destroy a norm. What matters is how people respond to it.

And you’ll notice something strange about this episode. It’s not as if Syria is defending their use of chemical weapons. They’re denying it. And that helps contribute to the notion this is an unacceptable process. In World War I, the Germans argued that gas might be more humane than bayonets or getting blown up. Some people think that the Bush administration’s view on enhanced interrogation techniques struck a real blow against norms against torture. No one is defending chemical warfare. All the dynamics here have served to highlight that this is a salient norm in global politics today.