Signing into law the National Defense Authorization Act for Fiscal Year 2017, outgoing United States President Barack Obama added further complexity and potentially explosive uncertainty to China-US relations.

The 2017 NDAA merits particular vigilance on Beijing's part because, for the first time in history, it includes a section on high-level military exchanges with Taiwan. Section 1284 of the act obligates the US Defense Secretary to carry out a program of exchanges with the island involving senior military officers and senior officials. This permits generals or flag officers of the US armed forces on active duty, as well as Pentagon officials above the level of assistant defense secretary, to visit the island.

On the surface, a stipulation like this may seem more symbolic than substantive. After all, on its own, sending higher-ranking officials and officers to the island does not change the nature of exchanges, as long as longstanding agreements, written and tacit alike, are observed.