In 2021, Attorney General Merrick Garland established new, but long-needed, press protections barring federal prosecutors from purasuing journalists’ communication records with confidential sources except in extreme circumstances. But these protections are only as good as the administration controlling the Justice Department.

President-elect Donald Trump, who has espoused hostility toward journalists and seeks to elevate people who share this feeling to powerful positions in government, is weeks away from taking over federal law enforcement agencies. In other words, Congress has little time left to codify Mr. Garland’s policy into law. The Senate can — and should — do that in the lame-duck session.

In January, the House of Representatives passed such a bill without opposition. The legislation — the Protect Reporters from Exploitative State Spying Act, or Press Act — would prevent the federal government from using legal tools such as subpoenas and search warrants to go after reporters’ information, except in cases where doing so would prevent violence or terrorism. The measure would also bar prosecutors from demanding that third parties, such as phone companies or internet providers, hand over journalists’ data.

That legislation has since languished in the Senate, but a spokesperson for Sen. Charles E. Schumer (D-New York) said the majority leader supports the bill and intends to pass it. Two conservative Republicans — Lindsey Graham (South Carolina) and Mike Lee (Utah) — already support the bill, and there are probably a few others who would like to see it pass, given the broad bipartisan support it has enjoyed in previous years.

The trouble, however, is Mr. Trump. Last month, he posted an all-caps demand on Truth Social that Republicans “KILL” the bill. Although his decision to weigh in on the legislation was unexpected, his opposition is unsurprising, given his first administration’s efforts to root out government leakers by obtaining the phone and email records of reporters at multiple outlets, including The Post. His Justice Department even obtained a gag order preventing executives at the New York Times from informing editors at the paper that the government was seeking the email logs of four reporters to uncover their sources.

The president-elect’s social media missive makes it less likely that Republican senators who support the measure will back it now, but they should keep in mind that this is not a partisan issue. Administrations from both parties have pursued journalists’ sources in recent years, including the Obama Justice Department, which seized phone records of the Associated Press in 2013 and conducted electronic surveillance of Fox News’s James Rosen in an aggressive attempt to expose leakers.

Such overreach disserves the public, regardless of whether it happens under a Democratic or Republican president. Confidential sources have been critical to exposing government abuses, such as the CIA’s waterboarding of al-Qaeda prisoners. One Pulitzer Prize-winning report from Mississippi Today’s Anna Wolfe relied on confidential sources to uncover the misuse of welfare funds in the state; now she and her editor face a court order to give up their sources or risk jail time. If journalists cannot protect their sources’ identities, whistleblowers might be unwilling to reveal information the public deserves to know.

Critics of the bill, such as Arkansas Sen. Tom Cotton (R), contend that it would encourage more government leaks, potentially damaging national security. But over the past few years, Mr. Garland’s rules do not appear to have increased controversial leaks or damaged national security.

Meanwhile, the need to protect journalists is as clear as ever. Kash Patel, whom Mr. Trump has chosen to replace Christopher A. Wray as FBI director, has said he would “come after the people in the media who lied about American citizens, who helped Joe Biden rig presidential elections.” He added, “Whether it’s criminally or civilly, we’ll figure that out.”

State and federal government accountability systems are more developed than they used to be, but they still often fall short. When they do, responsible media remain essential outlets for whistleblowers and other public-spirited individuals seeking to expose official wrongdoing. That will be true under Mr. Trump, but also under the next Democratic president. Mr. Schumer should stay firm in his stated intention to advance the Press Act before this Congress’s session ends — and the Republicans who understand its merits should support it.