Republican and Democratic lawmakers who remain bitterly opposed about expanding gun-control measures are banding together to demand that federal agencies comply with existing ones, after reports indicated that the gunman who killed 26 people in a church shooting in Texas should have been prevented from buying a firearm.

The Senate’s second-highest-ranking Republican announced Tuesday that he was planning to file legislation aimed at forcing federal agencies to upload required information about infractions into the National Instant Criminal Background Check System (NICS), and incentivizing state governments to do the same.

“Their record of compliance is lousy, it’s lousy,” Sen. John Cornyn (R-Tex.) complained on the Senate floor, describing the numbers of reports being filed as “staggeringly low.”

Cornyn was citing NICS statistics from late 2016 that showed many agencies, including many branches of the military, have reported zero felonies, domestic violence misdemeanors or restraining orders, indictments or other areas of concern to the NICS database.

Sen. Jeff Flake (R-Ariz.) also announced Tuesday that he was joining forces with Sen. Martin Heinrich (D-N.M.) "to prevent anyone convicted of domestic violence — be it in criminal or military court — from buying a gun," Flake tweeted Tuesday.

President Trump, who is traveling in Asia this week, has been silent on the proposals. His son, Donald Trump Jr., responded to Flake's effort by ridiculing it Tuesday, tweeting that Flake's bill was "incredibly proactive considering that law has been on the books since the mid 90s."

But the senators’ complaint is that the federal agencies have not been complying with the law and that the military is exploiting a loophole that lets them report domestic assault as indistinct from other assaults — unlike the reporting requirements for state courts.

“There has only been one instance, just one, of military reporting a charge like this to the database,” Flake told reporters Tuesday, referring to domestic violence. His bill with Heinrich would “simply clarify and actually force the military to take anything that would have been a domestic violence conviction to the state court and report it as such to the NICS system,” Flake said.

While it is not clear how many incidents have been omitted from the NICS database, lawmakers were convinced that the Texas gunman could not be an isolated case.

“This is only one example of repeated and frequent failures to report required convictions,” said Sen. Richard Blumenthal (D-Conn.). Blumenthal sent a letter to Defense Secretary Jim Mattis on Tuesday requesting a full accounting of how the Pentagon turns over such information to the FBI, as well as how the military prosecutes domestic violence cases.

Sen. Kirsten Gillibrand (D-N.Y.) also wrote to Mattis on Monday, requesting that he “immediately initiate an audit of all military criminal investigative organizations” going back 10 years, and focusing on cases “in which the military was required to notify the Federal Bureau of Investigations of the outcome.”

Democrats have long argued for expanded background checks but sidelined those demands Tuesday in an effort to focus on improving compliance with current laws.

“Let’s fix the background check system so that, as Republicans tell us over and over and over again, at least we can enforce existing law,” Sen. Chris Murphy (D-Conn.) said on the Senate floor. Murphy has emerged as one of Congress’s most vocal advocates for gun control, frequently referencing his home-state example of the Sandy Hook school shooting in Newtown, Conn. The aftermath of that shooting was the last time the Senate came close to passing a gun-control measure.

Cornyn, a staunch critic of that and several other gun-reform measures, offered Tuesday to work with Murphy to force the federal government to improve its reporting.

The background check system “failed us terribly here,” Cornyn said, adding that current reporting practice of agencies “is unacceptable and it must change.”