In a 1949 Supreme Court case, Justice Robert H. Jackson wrote a famous dissenting opinion warning that the Constitution’s Bill of Rights is not “a suicide pact.” He meant that the First Amendment does not absolutely protect speech and should not be seen as preventing the government from maintaining ordered liberty.

Whether or not Justice Jackson was right about that particular case or that specific understanding of the First Amendment, his words ought to serve as a practical reminder in other contexts as well. For instance, we are not compelled to play the role of passive spectators while unforced errors by one branch of the federal government create a national emergency. The Constitution provides tools necessary for national self-preservation and does not prevent us from taking the kind of action needed to respond to a crisis.

Americans face such a crisis today. Donald Trump’s presidency is careening out of control. U.S. markets are having their worst month in decades. Investors may be rattled by any number of events or concerns, including a government shutdown, reports that the president has considered firing Federal Reserve Chairman Jerome Powell, a strange Treasury Department statement that Secretary Steve Mnuchin has been checking in with the CEOs of major banks to confirm they have ample liquidity, and of course the ongoing trade war with China.

Investors and non-investors alike took notice when Secretary of Defense James Mattis resigned. Former George W. Bush aide Michael Gerson reports that one Republican senator said simply: “we are in peril”. Gerson tweeted that “many in DC, including [Republicans are] now unsure if [the Trump] administration can be relied upon to carry out its most basic [national security] duties.” Tom Nichols of the Naval War College wrote that “our enemies are [now] openly gloating.” In recent weeks, we have read publicly available excerpts from heavily redacted court filings related to the prosecution of Trump insiders Michael Flynn, Michael Cohen, and Paul Manafort. These documents make clear that the president faces the possibility of impeachment and legal jeopardy related to his involvement in criminal activity. We know that there is more to come, and that the president will continue trying to interfere with or even shut down Robert Mueller’s investigation.

Alarm bells are ringing, loud and clear. But at least two things must happen before there can be an appropriate response. First, Republicans in Congress must recognize the danger. Second, they must be willing to act, using the constitutional tools available to them.

There are signs that Republicans understand the urgency. The Republican senator who spoke with Michael Gerson would not make his concerns public, but other Republicans are doing so. Sen. Marco Rubio (R-FL) said that Mattis’s resignation letter made it “abundantly clear that we are headed towards a series of grave policy errors which will endanger our nation, damage our alliances & empower our adversaries". Sen. Lindsey Graham (R-SC), typically a staunch Trump ally, warned that “if we continue on our present course, we are…paving the way toward a second 9/11”.

“ It’s not clear whether Republicans fully appreciate their own power as members of a co-equal branch of the federal government. ”

Yet the time for statements of concern has long since passed. Are congressional Republicans ready to use any of the tools available to them under the Constitution? That remains unclear. In fact, it’s not clear whether Republicans fully appreciate their own power as members of a co-equal branch of the federal government. Sen. James Inhofe (R-OK) worried about Mattis’s departure but said “I’m not sure what options we have.” Sen. Deb Fischer (R-NE) asked “What would you suggest? The president is commander in chief, and he will ultimately make these decisions; it’s my job to either support those decisions or to raise concerns.”

Actually, Sen. Fischer and her colleagues can do much more to rein in Trump — if they choose to act. They can hold hearings. They can refuse to confirm nominees. They can pass legislation — for instance, to protect Mueller. They can stop going along with the president’s agenda— for example, by moving ahead with legislation to end the shutdown, over the president’s veto, if necessary. Finally, they can consider impeachment and removing Trump from office — something conservative commentators are starting to suggest.

We can all see what is happening in front of us. As Thomas Wright observes, Trump’s growing sense of desperation means that “[n]othing can be ruled out anymore” when it come to the president’s actions. That is a sobering observation when one considers the immense power available to the office — especially when and if a president decides to push authority to the limit, or even past Constitution’s the paper boundaries.

It is essential to emphasize that the same Constitution providing Trump with broad power also provides members of Congress with the power to set limits on what he can do, to change course as the nation heads into increasingly dangerous waters. Paper boundaries are just that if Congress passively defers — but those same boundaries become hard and fast barriers in the hands of legislators who are determined to act.

The alarm bells are ringing. The question now is not just whether we will hear them and take action, but whether it will be too late.

Chris Edelson is an assistant professor of government in American University’s School of Public Affairs. He is the author of “Power Without Constraint: The Post 9/11 Presidency and National Security” (University of Wisconsin Press, 2016).

Read more: Mnuchin can’t stand up to his boss — and it’s costing you money