Given that the ATT called for heightened scrutiny of arms sales in cases where they "could be used to commit or facilitate serious violations of global humanitarian or human rights law, acts of terrorism, or transnational organized crime", ratifying it would likely have put the spotlight on the end users of American weapons worldwide.
United Nations spokesman Stephane Dujarric said in a statement that the treaty that the White House is choosing not to ratify is "a landmark achievement in the efforts to ensure responsibility in global arms transfers".
The 193-nation U.N. General Assembly overwhelmingly approved the pact in April 2013. However, some supporters of the President and the NRA feel that protesting the NRA is the wrong way to do it.
Speaking at the event his third straight year, Trump declared himself a "champion for the Second Amendment".
Rachel Stohl, managing director of the Stimson Center and a consultant to the UN Arms Trade Treaty process, dismissed Trump's withdrawal from the treaty as stagecraft created to please his allies in the gun lobby. United Nations officials said they were unaware Trump had been planning to revoke the USA signature.
On stage in Indianapolis, Trump then signed a formal message to the Senate asking lawmakers to "discontinue the treaty ratification process". And it represents just the latest in a series of withdrawals from worldwide pacts and organisations joined by previous administrations, like the Paris climate accord and the Iran nuclear deal.
Ratifying the treaty would also allow rival arms exporters like Russian Federation and China - neither of whom have signed the agreement - to cut into the US' market, a point explicitly laid out in the White House's argument against the treaty.
With Friday's announcement, Trump continued his drive to roll back Obama-era initiatives.
Almost two years ago, Mr Trump announced that the United States would withdraw from the Paris Climate Agreement, which aims to reduce global carbon emissions that scientists link to harmful climate change. Republicans argue the USA economy would suffer if it met the deal's carbon-reduction goals.
He added: "This isn't a joke, this is serious and one could continue but I listen very carefully to what's coming out of the united states".
North left the annual meetings, which are being held in Indianapolis this weekend, early on a plane to Washington D.C. Friday night. It was outspent by gun control groups in the 2018 midterm elections.
Since the last convention, Trump has shown support for a new federal law banning bump stocks and other devices that convert a semi-automatic weapon into a fully automatic machine gun.