Saletan: Is water more dangerous than weed?

This is an archived article that was published on sltrib.com in 2014, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

WASHINGTON - "Among the many oddities that have arisen from marijuana legalization in Washington and Colorado is this: It can be easier to get through airport security with a bag of weed than a bottle of water."

That's the opening sentence of an Associated Press dispatch this week from Colorado. The article goes on to explain: "The Transportation Security Administration makes travelers empty their water bottles, but when agents encounter personal amounts of marijuana at security checkpoints, they typically don't call the DEA or FBI."

This is madness, right?

Wrong. It's perfectly sane. In fact, it illustrates how strange the world can seem to us when our intuitions and traditions are replaced by rationality.

TSA limits carry-on containers of any liquid, including water, to 100 milliliters, i.e., 3.4 ounces. That's because of a 2006 plot to blow up planes using "liquid explosives disguised as commonly consumed UK beverages." In 2010, TSA administrator John Pistole indicated that the plot may have involved "sodas and water." The problem, he explained, "is that liquid explosives don't look any different than regular liquids on the X-ray monitor."

Why, then, doesn't TSA forbid all water? In 2008, then-TSA administrator Kip Hawley reported that lab tests determined the 100 milliliter threshold adequately "limits the effect of, and even the ability of, a detonation." He added: "We try to prohibit the minimum possible from a security standpoint. Also, the consequence of banning all liquids is a large increase in the number of checked bags, which creates its own issues."

In other words, airport security involves tradeoffs. Every second TSA officers have to spend on marginal threats such as pocket knives and small liquid containers is a second they're distracted from more serious possibilities.

That's why it can be, and should be, easier to get through airport security with a bag of weed than a bottle of water. Unless you've figured out how to disguise a plane-exploding bomb as an ounce of pot, your baggie isn't worth a TSA officer's time.