If a group of senators gets its way, any commitments President Obama makes at the Paris climate summit will be put to a congressional test.

But first, the mainly Republican lawmakers must prove that the product of the Paris meeting is effectively a treaty – and that is a legal hurdle they may not be able to clear.

World leaders are gathering in Paris starting Monday to attempt to seal an international deal to curb greenhouse gas emissions and slow climate change. If given the opportunity, the Republican-led Senate would almost undoubtedly reject such a deal.

President Obama doesn’t plan to give it the chance. Whatever agreement emerges from Paris, he has no intention of submitting it to the Senate for ratification as a treaty. The administration argues that any agreement does not bind the United States to a course of action. Moreover, it says the Clean Air Act and the United Nations Framework on Climate Change signed by former President George H.W. Bush already give Obama the authority he needs to carry out climate commitments.

There are disadvantages to that approach: a new president could back away from the Obama climate plan. A treaty would bind all future presidents to comply with it. For now, however, even without formally signing an agreement, the Obama administration is expected to abide by its own policies aimed at reducing carbon emissions by 26 to 28 percent below 2005 levels by 2025.

“The Senate has already had its say,” said Nigel Purvis, founding president of consulting firm Climate Advisers and a former State Department treaty lawyer under Presidents Clinton and George W. Bush.

“The basic rule is if an international agreement doesn’t require a change in U.S. law, if the president has the authority to implement the agreement with existing law, you don’t need to send it to Congress for approval,” Purvis said. He added that presidents since George Washington had joined “executive agreements” without seeking Senate approval.

But senators challenging the president aren’t buying that argument.

Earlier this month, Sens. Jim Inhofe (R-Okla.), Roy Blunt (R-Mo.) and Joe Manchin (D-WestVa.) introduced a sense-of-the-Senate resolution insisting the president seek the Senate’s advice and consent on “any protocol, amendment, extension or other agreement” reached at the Paris conference.

“Should the negotiations produce a more substantive outcome as European delegates announced, then there is no way around the Senate,” Inhofe said in a statement. “I would urge caution in considering any diplomatic promises that may suggest otherwise as the president is once against attempting to make international promises he cannot deliver.”

That Inhofe, Blunt and Manchin would spearhead a campaign to check the president’s authority to implement climate change commitments is not surprising: Inhofe, the chairman of the Senate’s Environment and Public Works Committee, is a vocal climate change skeptic, while Blunt and Manchin have worked actively to protect the coal industry.

If an agreement were to end up in the GOP-controlled Senate, rejection would be its most likely fate. That would would be a setback for Obama and for international momentum on the climate issue, but it would be consistent for Republicans who have repeatedly skewered the president for what they view as his overreaching use of executive power.

In this case, their cause is tangled up in an international disagreement about whether any Paris agreement would be “legally binding” — and the meaning of the word binding.

The Paris agreement “will be legally binding with respect to some areas and not with respect to emission reduction commitments nations make,” said David Sandalow, a fellow at Columbia University’s Center for Global Energy Policy and a former senior National Security Council and Energy Department official working on climate issues.

The administration seems well aware that how the treaty is viewed in Washington is just as important as the perception of it abroad.

In a Nov. 11 Financial Times interview, Secretary of State John F. Kerry said that a Paris agreement is “definitely not going to be a treaty,” noting that there were “not going to be legally binding reduction targets like Kyoto” – a climate accord from the ’90s that was rejected by the Senate.

Those comments spurred a backlash from European governments, which are expecting the Paris conference to produce an internationally legally-binding instrument.

“The Paris agreement must be an international, legally binding agreement,” a spokeswoman for the EU’s climate commissioner, Miguel Arias Cañete, told the Guardian earlier this month. “The title of the agreement is yet to be decided, but it will not affect its legally binding form.”

French foreign minister Laurent Fabius suggested that Kerry was “confused” about the legal point. In the past, even he has acknowledged that in order for a Paris deal to work, it would have to rely on  presidential support  — without congressional approval.

Administration aides argue that any agreement, unlike the Kyoto protocol, would lack binding emissions targets.

“This is not an agreement where top-down emission targets are imposed in a binding way on countries,” a senior administration official said at an October briefing, explaining that the agreement would reflect “bottom-up country commitments” made voluntarily.

Other administration officials explain that the deal would “bind” countries to a process, not an outcome. Countries would have to submit climate action plans, as virtually all countries have, make those plans transparent and consult with others if targets are missed.

Plus, it would be hard to penalize countries for infractions of the deal — there is no equivalent of an international climate police, diplomats note.

A similar model was followed in an earlier international accord limiting mercury emissions. Senior Obama administration officials involved in negotiating that accord discussed among themselves the need to use the mercury pact to set a precedent for Paris, according to one of the officials involved but who asked for anonymity to protect relationships.

At the end of the day, the parties to the Paris agreement do not have to see eye-to-eye about how legally binding the agreement is in order to strike a deal.

“Every state controls whether that state is a party to a binding agreement, and in each case, that state’s intent controls,” said Michael Glennon, a professor of international law at the Fletcher School at Tufts University and a former Senate Foreign Relations Committee counsel. “The key word is intent: If the U.S. doesn’t intend to enter into a binding agreement and makes that intent explicit, then there will be no binding agreement that obliges the United States to do anything as a matter of law.”

If the president circumvents the Senate and uses his executive authority to make an international deal, it won’t be unprecedented, Glennon added, pointing to the Iran nuclear accord as a recent example. In that case, the administration resisted submitting it to the Senate as a treaty; ultimately, Congress wrote a unique role for itself into the process by passing a law creating special review power over the deal.

With a climate change agreement near, senators — most of them Republicans — are taking steps to insert themselves into this process as well.

On the same day as Inhofe, Blunt and Manchin made their announcement, a group of 30 Republican senators led by Mike Lee of Utah introduced a sense of the Congress resolution insisting the Obama administration submit to the Senate any climate agreements “whether deemed ‘legally binding’ or not” – especially ones that includes targets or timetables. The resolution also warns that Congress would refuse to budget any money for the Green Climate Fund until all such agreements are submitted to the Senate.

Obama proposed giving $3 billion a year to the fund to help countries meet targets set in Paris, but many Republicans would like to block the move. More than 100 House lawmakers signed a letter to Appropriations Committee leaders earlier this month, opposing Obama’s request for the Green Climate Fund.

Inhofe and John Barrasso (R-Wyo.) circulated a similar letter addressed to Obama in the Senate, promising that “Congress will not allow U.S. taxpayer dollars to go to the Green Climate Fund until the forthcoming international climate agreement is submitted to the Senate for its constitutional advice and consent.”

In the end, compliance with any agreement will come down to national will and international pressure.

“What does legally binding mean in an agreement that is not going to have financial penalties for non-compliance?” asked Paul Bledsoe, an energy consultant and former climate policy aide in the Clinton White House. “In the World Trade Organization, it is hard enough – and that does have penalties.

“The bottom line is it’s not going to be a treaty,” Bledsoe said. “The United States is not going to agree to anything that requires Senate confirmation. And that’s that.”