When President Barack Obama announced his intention to close the Guantanamo Bay detention center on his second day in office, he sounded serious.

He was flanked by more than a dozen retired military leaders, who’d all urged him to close the facility because it had become a virtual recruitment tool for terrorists and a stain on the United States’ reputation for upholding human rights and the rule of law. Obama also had the support of national-security experts across the political spectrum when he signed his historic executive order.

More than six years later, the U.S. facility in Cuba is still open. The primary reason is that ever since the president made it a priority to close Guantanamo, congressional Republicans made it a priority to keep it open. They’ve even stepped up their efforts while writing the annual defense authorization bill this year.

Leg shackles are seen on the floor at Camp 6 detention center, at the U.S. Naval Base, in Guantanamo Bay

Obama has again threatened to veto the bill over these obstructionist tactics. But unlike previous years, if he’s going to keep a key promise he made when he entered the White House — one he said “would further the national security and foreign-policy interests of the United States and the interests of justice” — he has to follow through.

Over the years, Congress has passed a series of onerous restrictions on transferring Guantanamo detainees to other countries, and since 2010, a complete ban on bringing any to the United States, even for trial. This even though such prominent Republican leaders as Senators John McCain (R-Ariz.) and Lindsey Graham (R-S.C.) have, in the past, supported closing the facility for national-security reasons. And even though the U.S. federal courts’ record for prosecuting terrorists is far stronger than the record of the fledgling Guantanamo military commissions. Federal courts have prosecuted more than 500 people on terrorism charges in the 13 years since the Sept. 11 attacks; the commissions haven’t yet managed to bring the five accused plotters of the attacks to trial.

Now, facing the second half of Obama’s second term, Congress has gone even further: The House and Senate Armed Services Committees have proposed such draconian restrictions on transferring the detainees that, if enacted, Obama would never be able to close the prison.

The House version, for example, would not only prevent detainee transfers to the United States, but it would also ban transfers to any place the Internal Revenue Service labels a “combat zone,” a term not based on danger level but devised for purposes of giving servicemembers a tax break. These are locations, established by executive order, where “the U.S. Armed Forces are engaging or have engaged in combat.”

That’s a wide swath of territory. “Combat zones” include such places as Albania and Bosnia-Herzegovina — U.S. allies where the United States hasn’t been engaged in active hostilities for more than a decade and that have already safely resettled more than a dozen Guantanamo detainees.

File photo of detainees sitting at Naval Base Guantanamo Bay

The president shouldn’t stand for that. As commander in chief, he’s responsible for protecting the nation and carrying out an effective foreign policy. He and many others have made clear that closing Guantanamo is critical to these goals. He should veto any legislation that comes out of Congress that would thwart them.

Although the Senate Armed Services Committee on Thursday passed a bill that McCain said would provide a path for closing Guantanamo, it does not lift transfer restrictions. It requires instead that the Obama administration first propose a plan for closing the facility for Congress to accept or reject. Yet, given its stance over the past six years, and the recent House bill, there is no reason to believe Congress would approve any plan Obama put forward.

No president likes vetoing an authorizations bill, of course, because that’s how important agency and department budgets get set. But it would hardly be unprecedented. President George W. Bush vetoed the defense authorization act in 2008 on the grounds that it would imperil the economic security and reconstruction of Iraq, a major goal of his presidency. President Bill Clinton vetoed the bill in 1996 because, among other things, it would have restricted the president’s ability to conduct contingency operations. Obama has repeatedly threatened to veto the act, but each time Congress agreed to minor legislative changes. And he signed it.

This time, the president needs more than minimal tinkering to address a law that would block a cornerstone of his national security policy. Unless Congress agrees to withdraw the restrictions entirely and work with the president to finally shutter the Guantanamo detention center, the president should follow through with a veto.

What makes this time different?

Congress has grown ever bolder in its efforts to defy the president in what its critics say is a concerted effort to undermine Obama’s and his party’s legacy, which some Republicans insist is a radical left-wing agenda that will “endanger America.”

Though there’s no way to take politics out of governance, it’s gotten to the point where that defiance is interfering with Obama’s ability, as commander in chief, to protect the nation.

Obama has shown he is willing to make bold moves when it comes to issues he cares about, including immigration and raising the minimum wage. The president doesn’t have much time left when it comes to one of his key national security initiatives — closing Guantanamo.

He should wait no longer.  Now is the time.