It did not attract a ton of attention at the time (nothing does these days) but about a year ago on February 28, 2017, Congress passed and Donald Trump signed a law revoking an Obama-era regulatory initiative that made it harder for people with mental illness to buy a gun.

Yet despite this effort to roll back even a very modest effort to restrain the ability of seriously incapacitated people from obtaining deadly weapons, this morning Trump tweeted that there were “so many signs that the Florida shooter was mentally disturbed,” implying that someone should have done something to report him.

So many signs that the Florida shooter was mentally disturbed, even expelled from school for bad and erratic behavior. Neighbors and classmates knew he was a big problem. Must always report such instances to authorities, again and again! — Donald J. Trump (@realDonaldTrump) February 15, 2018

But it’s Trump’s party — and Trump himself — who have consistently prevented the federal government from doing anything about this kind of situation. The Obama-era gun regulation wouldn’t have had a massive impact on gun violence in the US since it’s estimated that it would only affect about 75,000 people. And disability rights groups had their own objections to the bill so some liberal groups, including the ACLU, joined with the National Rifle Association in urging Trump to reverse it.

But anything that makes it easier to obtain a gun, the research suggests, will likely worsen gun violence. After all, America already has some of the weakest gun laws in the developed world — and repealing a rule that made it a little tougher for some people to buy a gun likely makes that worse.

The rule tasked the Social Security Administration with turning over information to the FBI

The vote was part of a larger suite of Congressional Review Act measures that passed early in the Trump administration. The CRA allows Congress to overrule recently enacted regulatory initiatives passed by the executive branch. CRA bills can’t be filibustered, but they do need to be signed by the president.

Consequently, the CRA is rarely used since the president isn’t going to sign a measure blocking his own regulations. But in the first year of the Trump administration, the CRA was used to reverse a whole suite of final-year Obama regulations. These reversals mostly made life easier for polluters but also let Internet Service Providers sell your web browsing data to advertisers and made it easier for people with severe mental illness to buy guns.

Specifically, what Obama did was order to Social Security Administration to take the list of people who were deemed so severely mentally ill that they are unfit to handle their own disability benefits and forward it to the FBI. The FBI was then supposed to incorporate that list in the background checks used to disqualify people from gun ownership.

This is obviously an extremely narrow measure that wouldn’t have had enormous impact one way or the other — it just represented Obama’s limited capacity to do anything on guns in the face of relentless congressional opposition.