Under Unites States law, the president must certify two things with respect to the Iran nuclear deal every 90 days: (1) that Iran is in compliance with the deal, and (2) that the deal remains vital to US security interests.

When President Donald Trump failed to certify the Iran deal (the Joint Comprehensive Plan of Action, or JCPOA) last week, he didn’t specify which of the two certification aspects he was acting on. But since the US military and intelligence communities are unanimous in their opinion that Iran is in compliance, it is reasonable to conclude that the second certification was on the president’s mind, according to experts who spoke yesterday at Columbia University’s School of International and Public Affairs.

“The argument is that the nuclear deal itself is not good enough,” said Richard Nephew, a former sanctions policy coordinator at the State Department. “There are provisions in the deal that expire and it doesn’t address non-nuclear issues.”

Some say the president could have withdrawn the US from the deal altogether, but clearly didn’t do that last week. That means it’s up to Congress to take some sort of action with respect to the deal—or not.

The JCPOA implementing legislation includes expedited parliamentary procedures for re-imposing nuclear sanctions against Iran. Some members of Congress are currently talking about taking some limited actions against Iran without reimposing the full sanctions. But the consensus of experts is that anything short of a full sanctions snap-back would not qualify for the expedited procedures, according to Avril Haines, a former Obama White House and CIA official.

In other words, if Congress is inclined to act against Iran—and that’s not at all clear at this point—it’s going to take a while to get anything done.

Either way, the Congressional agenda is going to bump up against the next set of presidential JCPOA actions. You see, the 90-day certifications aren’t the only actions required by law. Every 120 days, the president must issue a waiver on the Iranian oil industry and every 180 days he must consider waiving sanctions on the country’s financial institutions. Both of those sets of waivers come due in January 2018.

Given the president’s pronouncements on JCPOA, that would seem to give Trump little wiggle room. “But he could make the argument that while the deal is not in the US national security interest, neither is reimposing nuclear sanctions,” said Nephew.

Uncertainty over the upcoming 120-day oil industry sanctions, given Trump’s rhetoric, has already injected a significant level of political risk into decisions on international investments in Iran.

“The market now has to deal with this as a clear and present danger,” said Helima Croft, head of commodity strategy at ‎RBC Capital Markets. “Trump’s rhetoric adds to concerns over the outlook for energy investments in Iran.”

The Iranians were counting on the lifting of nuclear sanctions to accelerate the growth of their economy. Until recently, the political risk premium was zero, according to Croft, but now investors have to divine what Trump might have in store in January.

European investors have expressed a “level of uncertainty about the risk,” she said, “especially if they not able to raise capital in the US.”