The Hong Kong government has limited the amount of baby milk formula that people can take with them when leaving Hong Kong to two cans per person, but is thereby risking violating Article XI:1 of the General Agreement on Tariffs and Trade (GATT), as the rule could also block commercial exports. Bryan Mercurio, Professor of Law at Chinese University, said the rule was an illegal export restraint. In practical terms, there is little chance the measure would be challenged as the mainland is unlikely to invoke WTO dispute proceedings against Hong Kong, while other countries are unlikely to have sufficient interest to do so. The two-tin limit was enacted to curb a shortage of baby formula in the city, widely blamed on large-scale re-exports to the mainland. Parallel traders profited by reselling the formula on the mainland, where much heavier taxes are levied on imports of legitimate baby formula, and domestic brands are widely mistrusted. Under Hong Kong’s new law, would-be exporters of baby milk formula must apply for an export license from the Trade and Industry Department. The Hong Kong government said that “GATT expressly allows [the] application of temporary export prohibitions and restrictions to prevent or relieve critical shortages of foodstuffs or other products essential to the exporting member.” At least 45 people have been arrested so far as they attempted to cross into the mainland with more than the permitted amount of infant milk formula. They included 26 Hong Kong residents and 18 mainlanders. One person had a foreign passport. Eight of those arrested were cross-border drivers.