This morning, the U.S. International Trade Commission issued an affirmative determination in a so-called “Section 421″ or “China-Specific Safeguard” case that imports of consumer tires from China are causing market disruption in the United States. That may sound like just another day in Washington, but the decision could very well be the catalyst for the most consequential event in trade policy since the Bush steel tariffs of 2002. It will certainly force a defining moment for a president who has preferred obfuscation to clear direction on trade policy.

Under the statute (which became U.S. law as a condition of China’s accession to the World Trade Organization in 2001), the ITC has 20 days to provide remedial recommendations to the president and the U.S. trade representative. Those recommendations are likely to include quotas, tariffs, or some combination that will ultimately curtail the supply and raise the prices of all tires in the United States — not just those imported from China. However, the president has the discretion to deny import “relief” if he determines that such restrictions would have an adverse impact on the U.S. economy that is clearly greater than its benefits, or if he determines that such relief would cause serious harm to the national security of the United States.

I will forego my own explanation as to why restrictions would have an adverse impact that is clearly greater than its benefits, and instead give you the statement of the U.S. Tire Industry Association, which represents “all segments of the tire industry, including those that manufacture, repair, recycle, sell, service or use new or retreaded tires, and also those suppliers or individuals who furnish equipment, material or services to the industry.” Suffice it to say that no producers of tires in the United States supported this petition, so it is not a matter of U.S. tire producers against Chinese tire producers. It is really nothing more than a matter of a U.S. union objecting to management’s decision to produce its lowest grade (lowest quality, lowest priced, lowest profit margin) tires abroad. Yet the consequences of trade restraints could affect interests across and throughout the economy, particularly if China responds in kind.

During the Bush administration, there were six Section 421 cases filed by domestic parties, four of which were found by the ITC to warrant import relief. In each of those four cases, President Bush exercised his discretion to deny relief. The tires case is a test case for President Obama. Will 421 fly under this president? Or will it remain the dead letter that petitioners considered it to be under President Bush?

The stakes are much higher for Obama than they were for Bush because the unions (the United Steel Workers union is the petitioner in the tires case) and the Chinese both feel more emboldened in their positions now. Bush didn’t win the near-unanimous support of organized labor in his elections, nor did he promise to get tough on Chinese trade practices, as Obama did.

Instead, Bush set the precedent of denying relief. And he did it four times. So, the Chinese see this firmly as a matter of presidential discretion — unlike antidumping or countervailing duties, which run on statutory auto pilot without requiring the president’s attention or consent. In other words, although there are over 50 outstanding U.S. antidumping and countervailing duty orders against various Chinese products, none of them is considered to reflect the direct wishes of the U.S. president, and thus don’t rise to the level of a potentially explosive trade dispute. But trade restraints under the 421 will no doubt be considered by the Chinese to be a directive of the U.S. president, thus the offense taken and the consequences wrought could be profound.

The good news is that President Obama will finally be forced to take a stand — to match his words and deeds. After a campaign in which trade was disparaged, President Obama’s first 100 days were characterized by a conciliatory tone and some enlightened actions. He told the Mexican president and the Canadian prime minister that he no longer wanted to reopen NAFTA. He spoke out against the most protectionist provisions of the Buy American language in the so-called stimulus bill. He repudiated protectionism and pledged to avoid new protectionist measures at the G‑20 and before other international gatherings. His Treasury Department declined to label China a currency manipulator. And his trade representative set about articulating a pro-trade agenda, including support for a push to pass pending bilateral trade agreements and concluding the Doha Round.

But there’s been very little follow through and trade partners are beginning to doubt his sincerity. Efforts to schedule votes on pending trade agreements have been shunted aside as too controversial to happen before health care reform legislation. In the meantime, imports are being turned away from U.S. procurement projects on account of some mindless Buy American caveats and overzealous interpretation of other Buy American rules by project administrators, which is inciting copycat rules in Canada and China.

The time has come for the president to stop wavering and to take decisive actions on trade policy. Of course, he will have until September 17 to render his decision about whether to grant or deny relief in the tires case. Between now and then he should conclude that trade restrictions are not the appropriate course — that among other problems, they will also undermine his economic and diplomatic objectives. And while he’s denying relief, he should take some advice from Scott Lincicome and me to speak the truth about trade to those constituencies who will feel betrayed. Directly and honestly making the case for trade to those who doubt is more durable than rationalizing each pro-trade decision, which has been the norm for too long in Washington. Besides, the polls show that Americans have already turned the corner and are moving away from their misguided flirtation with protectionism. That may help inspire an uncommitted president to take the baton.