Banned in warfare, tear-gas is the default response to controlling protests

AS THE PROTESTS in Hong Kong drag on, rituals are coalescing. One oft-repeated rite might be dubbed “the unfurling of the banner”. As confrontation looms, from the masked ranks of police two step forward bearing a sign reading “Warning: Tear Smoke”, in Chinese and English. Then the firing starts, and clouds swirl, stinging and choking. Aside from a few wearing masks, the crowd scatters, with the police in pursuit.

Many demonstrators have experienced something like it. Indeed, Hong Kong is a relatively modest user. In the first five months of protests, its police fired nearly 6,000 rounds of tear-gas—far fewer than were used in Paris in a single day last December against gilets jaunes (yellow-jacket) protesters.

The term “tear-gas” covers a range of chemicals, of which the most widely used include o-chlorobensylidene malononitrile (CS), oleoresin capsicum (OC, or pepper spray) and 1-chloroacetophenone (CN). The gases are in fact powders. New variants are designed to disperse slowly.

Defenders claim that it saves lives. Tired, twitchy, scared cops armed with tear-gas will kill fewer people than those carrying only lethal weapons. After months of growing violence, only on November 8th did the protests in Hong Kong lead to a death. Alex Chow, a student, perished after falling...