U.S. Secretary of State John Kerry and Iranian Foreign Minister Javad Zarif shake hands as Omani Minister Responsible for Foreign Affairs Yussef bin Alawi and former E.U. top diplomat Catherine Ashton look on in Muscat, Oman, on November 9, 2014.National Journal

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The deadline for a nuclear deal with Iran is next Monday, and congressional opponents of an agreement are considering their options for preventing one from being struck. Congress has a wide range of tools it can use to get in the way of a deal with Iran—and President Obama has a few tricks he can use to counter.

A deal with Iran faces stiff opposition from members of both parties, who are wary of an agreement that would provide Iran with substantial sanctions relief without requiring it to dismantle its nuclear program. Sen. Mark Kirk, a Republican from Illinois, and Sen. Robert Menendez, a Democrat from New Jersey, are spearheading the chamber's opposition to a deal. In a joint statement last week, they said they would challenge any agreement that did not require Iran to completely take apart its nuclear program. "We will work with our colleagues in Congress to act decisively, as we have in the past," the statement read.

The most obvious avenue available to Congress for blocking a deal is legislative action. Because the deal rides on sanctions relief, Congress can deprive the American negotiating team of its strongest bargaining chip by either imposing new sanctions on Iran or making it very difficult for the U.S. to keep any promise to roll back existing sanctions.

But any new sanctions legislation Congress passes would be, of course, subject to a presidential veto. Obama threatened to veto a bipartisan bill to impose new sanctions on Iran last December, and given that a deal with Iran is quickly becoming a legacy issue, he's likely to do what he can now to keep it alive.

To keep the president out of the picture, Congress could pass a nonbinding expression of congressional will, says Rudy deLeon, former deputy secretary of defense and a senior fellow at the Center for American Progress. A nonbinding resolution would make a point without creating an enforceable law that would require the president's signature.

Negotiations are so fragile, and each side's distrust of the other so deep, that a symbolic gesture could be just as effective as legal action. "It doesn't do any good as a legal matter for Congress to tell the president, 'Don't negotiate this agreement,' " says Dan Marcus, a fellow in law and government at American University. "But as a practical matter, it could have an effect." If Iran is worried that Congress will undercut a deal once it's made, or that a future president will back out, an agreement could fall apart before it's even implemented.

The existing economic sanctions on Iran come in two main forms. A good chunk of the sanctions regime was implemented by executive order, which makes it easy for the president to strip away whatever punitive measures he sees fit to end. But a number of the harshest sanctions on Iran were written into law by Congress and would require a congressional vote to repeal.

The president can intervene to provide temporary relief, but he would eventually have to involve lawmakers. "Congress, when it enacts sanctions, usually gives the executive branch some authorities for waiving them," says deLeon. "Remember: It was the administration that asked for the sanctions in the first place. But at the one-year mark, to take some of these elements off will require that there be legislation."

Another approach that's been floated to block a deal is to deny funding for necessary elements of the agreement. Sen. Lindsey Graham, R-S.C., has threatened to do just that if the White House tries to make a deal without involving Congress. But Marcus says that appropriations, usually one of the most effective weapons Congress wields, doesn't have so much clout here. "This is not something that requires a lot of money," he says.

Even as it puts up opposition to a deal, Congress has its own image to worry about. "Congress doesn't want to be viewed as having sabotaged a deal," says deLeon. Instead, it may want to wait until it's sure that a potential deal is unacceptable, even if the alternative is a return to the status quo, Marcus says. "Five years from now, when the Iranians are sitting there with their nuclear weapons and threatening their neighbors, the people who said 'let's wreck this deal' won't look so good."

This article is from the archive of our partner National Journal.

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