WASHINGTON — The mom of Desiree Robinson — the Chicago teen who was sold to her death on the Backpage.com — was at the White House on Wednesday as President Donald Trump signed a law aimed at curbing sex trafficking.

The law passed Congress overwhelmingly. It weakens a legal shield for online services that host abusive content, including sex trafficking.

After Trump signed the law, he handed one of the pens he used to Yvonne Ambrose, Robinson’s mother.

The body of Robinson, 16, was found in a Markham garage on Christmas Eve 2016 — her throat slit and her body beaten. Last week in federal court Charles McFee, 26, admitted to a judge he had delivered Desiree to an accused pimp in December 2016. That pimp is accused of shopping Robinson around on Backpage.com, a classified advertising website which, controversially, has included ads for sexual services.

Ambrose has sued Backpage.com and testified before the U.S. Senate last year in favor of the bill. Her attorneys issued a statement from her after the signing ceremony.

“I will live with the heavy pain of losing my sweet daughter every single day for the rest of my life,” Ambrose was quoted as saying.

“But, being at the White House to witness the signing of this monumental bill into law is proof that our fight against online sex-trafficking has made a change — a change that will save the life of someone else’s daughter. It is the change that Desiree deserves, and the one that she would have wanted for others. We refuse to be intimidated. We will continue to fight to save others from the horrors of online sex-trafficking and hold accountable every person responsible for these terrible and sickening crimes.

The protections signed by Trump Wednesday make users of such sites as Facebook liable for the content. The legislation grew out of frustration that classified-ad sites can claim they aren’t the publisher of questionable content but are merely transmitting posts by others.

Desiree Robinson

Desiree Robinson. | Provided photo

“Without Backpage, there’s no murder of Desiree,” Antonio Romanucci, Ambrose’s lawyer, said after last week’s court hearing in Chicago.

Antonio Rosales has been charged in state court with Desiree’s murder. The accused pimp, Joseph Hazley, faces federal charges for allegedly selling her for sex on the website. But a week ago, prosecutors finally secured the first conviction in her death when McFee admitted he delivered her to Hazley for a finder’s fee he apparently never received.

Then, last week, federal authorities also seized the Backpage website. Its founders, Michael Lacey and James Larkin, are accused in an indictment unsealed Monday of publishing ads that depicted children who authorities said were sex trafficking victims.

The indictment claims the website ignored warnings to stop running advertisements promoting prostitution because the lucrative enterprise brought in half a billion dollars.

Contributing: Sun-Times Staff Reporter Jon Seidel; Associated Press