While the Brett Kavanaugh drama was tearing apart Washington last week, Sen. Rand Paul (R-KY) quietly signed on to a Democrat-led bill prohibiting the use of federal money for a war against Iran without Congress’s express approval.

Paul’s signature officially makes the bill, introduced on September 26, a bipartisan effort to restrict America’s involvement in a potential conflict with Tehran.

The legislation would, however, allow for US military action against Iran without congressional approval “in response to an imminent threat to the United States” or “to rescue or remove United States citizens or personnel,” according to the text of the bill.

The Prevention of Unconstitutional War With Iran Act of 2018 is sponsored by Sen. Tom Udall (D-NM), and Paul becomes the ninth senator — and the first Republican — to put his name on the bill.

When contacted by Vox, Paul’s office declined to comment.

The legislation’s introduction last month came hours after President Trump chaired a meeting of the United Nations Security Council focused mainly on Iran and nuclear proliferation. The Trump administration has taken a hard stance against Tehran, removing the US from the 2015 Iran nuclear deal and reimposing sanctions on the country that the agreement previously lifted.

And last month, Trump used his speech at the UN General Assembly in New York to hammer Iran over its support for terrorism and aggression against US allies in the Middle East, ratcheting up the tensions between the two countries.

“Iran’s leaders sow chaos, death, and destruction,” Trump told the hundreds of world leaders gathered for the meeting. “They do not respect their neighbors or borders, or the sovereign rights of nations. Instead, Iran’s leaders plunder the nation’s resources to enrich themselves and to spread mayhem across the Middle East and far beyond.”

Iranian President Hassan Rouhani responded, claiming the US was responsible for “economic terrorism” toward his country.

Trump’s team repeatedly says it doesn’t seek any kind of regime change in Iran and that it wants to avoid a war, if possible. However, the administration also says that it wants Iran to change its behavior, remove troops and proxies from Syria, and stop interfering in Iraq’s politics partially by favoring Tehran-friendly candidates.

Still, senators like Udall and others — now including Paul — worry that a conflict with Tehran may not be far off if both sides continue their standoff.

“The Trump administration’s approach to Iran is ripped straight out of the same playbook that launched us into the failed invasion of Iraq, and Congress needs to assert its constitutional authority and halt the march to war,” Udall said in a statement when he introduced the legislation.

The president and his allies are “inching us closer and closer to conflict, endangering our national security, jeopardizing our diplomatic interests, and alarming our allies,” he said.

Congress is trying to reimpose its authority

The legislation faces an uncertain, but likely bleak, future.

First, the Senate Foreign Relations Committee must consider the measure and then pass it. If that happens, it could possibly make it onto the full Senate floor for a vote. And even if the Senate approves the measure there, it’s unclear if the president would sign the bill into law.

But even if the bill doesn’t become law, it’s the latest signal that Congress wants to curb the president’s power to unilaterally launch a war.

The Constitution says that Congress is the only governmental body with the power to declare war. But debate still swirls around whether a president can launch military strikes or even start a war without congressional approval, in part because some presidents say that being commander in chief gives the president unlimited authority to carry out military operations.

That’s why Udall felt it was worth putting forward the Iran legislation.

“The lives of American service members and the trajectory of US foreign policy should not be dependent on the whims of one president, Democrat or Republican,” he told me. Congress should act “as a check on the executive, urging restraint and diplomacy.”

A few members of Congress, like Sens. Bernie Sanders (I-VT), Chris Murphy (D-CT), and Mike Lee (R-UT), previously tried to claw back some of Congress’s control over wartime decisions.

In March, for example, those three lawmakers tried (and failed) to gain enough votes for legislation to stop US support for the Saudi-led war in Yemen. While the main reason was to end America’s participation in a horrible humanitarian catastrophe, it was also an attempt to reimpose Congress’s authority over whether and when the US goes to war.

And others, like Sens. Tim Kaine (D-VA) and Jeff Flake (R-AZ), have proposed legislation to make sure the president asks Congress for permission before starting any war.

Yet confronting Iran has become a bitterly partisan issue, with Republicans typically preferring a more aggressive stance while Democrats tend to prefer a diplomatic approach. It’s therefore likely that a Senate vote over the bill — both in committee and on the full floor — would split the chamber along party lines.

At a minimum, though, putting the bill forward may restart a decades-long conversation about what a war with Iran might mean — including the certain death of many US troops and thousands, if not hundreds of thousands, of Iranians.