Before the president signed the order, lawmakers from both parties, mindful of how frequently Trump reverses course - particularly on immigration, where he has repeatedly shifted positions within the course of hours - waited to see the details of what it would do.
It's unclear what will happen to the families that have already been separated.
The only other woman reportedly in the room was White House press secretary Sarah Huckabee Sanders, who was standing.
On Tuesday, Trump met with congressional Republicans, urging them to pass a border security bill that would amend the current laws, which the Department of Homeland Security says require them to house minors in separate facilities from their parents who are being charged with crossing the border illegally.
Widespread condemnation of US President Trump has greeted the recent flood of pictures and audio evidence of forcibly abandoned children crying for their parents.
The removals take place so that the parents can be prosecuted because the law forbids holding children in migrant detention for long period.
In the cases of repeat offenders or other serious criminals, children would be placed in the care and custody of the Department of Health and Human Services. Are any of your family members now being detained and kept apart?
'The morality of it was clear - that's not who we are, ' she said.
As Gutierrez spoke, his microphone was cut off because lawmakers and children gathered around him as he spoke.
The sole female invitee, according to a list sent out by the White House, was Representative Liz Cheney. We can enforce our immigration laws without breaking families apart.
He said he was looking into whether the court could block deportation of parents until they have been reunited with their children, and whether it could force the Trump administration to reunite those separated.
While Mr Trump held firm to his tough immigration stance in an earlier appearance on Tuesday, he acknowledged during the closed-door meeting that the coverage of family separations was taking a toll.
Images of undocumented immigrants, including children, being held in chain-link metal cages has stirred uproar and prompted some within Trump's Republican Party to break with the president on humanitarian grounds. But they are running up against Trump's shifting views on specifics and his determination, according to advisers, not to look soft on his signature immigration issue, the border wall.
Both Republican bills in the House, which Democrats and immigration advocacy groups have blasted, would fund Trump's border wall and reduce legal migration, in part by denying visas for some relatives of United States residents and citizens who are living overseas, sometimes referred to as "chain migration".
Trump insists that the only way to end the crisis is through Congress, putting pressure on the institution to agree to a slew of terms in exchange for a relaxation of policy at the border.
Trump told Republicans during a closed-door meeting Tuesday night that he would support them "1,000 percent" on immigration but did not specifically back either bill.
This ordeal is proof that Trump will literally do anything that Republicans support, and Republicans will support anything that Trump does. What happens after 20 days, the limit a court settlement now allows for children to be detained?
"Put simply, the deliberate separation of children and their parents who seek lawful asylum in America is wrong", the letter from the attorneys general reads, adding that the practice is "contrary to American values".