The law that bans gay and bisexual troops from serving openly in the military ended Wednesday with President Obama's signature.

“Thank you Mr. President,” someone in the crowd at the morning signing ceremony shouted as Obama approached the podium.

“You're welcome,” he replied.

Flanked by repeal backers, including Admiral Mike Mullen, outgoing Pennsylvania Representative Patrick Murphy, Speaker of the House Nancy Pelosi, Senate Majority Leader Harry Reid, and Senators Joe Lieberman of Connecticut and Susan Collins of Maine, Obama praised lawmakers and top military leaders who united to get the bill approved during a hectic lame-duck session of Congress.

In remarks before he signed the landmark bill, Obama said military service is no longer defined by sexual orientation and revealed that he had promised a young soldier he would lift the ban.

“Some of you remember I visited Afghanistan just a few weeks ago. And while I was walking along the rope line – a big crowd, about 3,000 – a young woman in uniform was shaking my hand and other people were grabbing and taking pictures. She pulled me into a hug and she whispered in my ear, 'Get don't ask, don't tell done.' And I said to her, 'I promise you I will.'”

“For we are not a nation that says don't ask, don't tell. We are a nation that says out of many we are one. We are a nation that welcomes the service of every patriot. We are a nation that believes all men and women are created equal. Those are the ideals that generations have fought for. Those are the ideals that we uphold today.”

Aubrey Sarvis, executive director of Servicemembers Legal Defense Network (SLDN), the largest group lobbying for repeal, praised Obama for backing the measure.

“In signing this bill today, President Obama delivered on a defining civil rights measure for our country and for gay, lesbian and bisexual members who have been silenced for far too long,” Sarvis said.

“President Obama was decisive and forceful in steering the course as he brought along critical stakeholders, including the Defense Department,” he added.

Implementation is expected to take months and supporters of repeal are cautioning gay troops not to come out yet.