It came at the close of a day of major changes announced by the president from pay freezes for staffers, to strict new limits on lobbyists, and promises of transparency.
After Tuesday's botched swearing in ceremony, some questioned the legitimacy of Obama's presidency, so Wednesday night inside the map room of the White House, the president retook the oath of office, just to make sure.
"We're going to do it very slowly. Ha, ha," said President Obama.
President Obama injected some levity before taking the oath of office again. Chief Justice John Roberts agreed to re-administer the oath after he flubbed the lines on Inauguration Day. This time, though, it went off without a hitch.
"That I will faithfully execute the office of President of the United States," said Obama.
Obama began his day in the oval office, where he read a good luck note left to him by President Bush. He then called leaders in the Middle East, before holding meetings with his top advisers about the two most critical issues he faces: the economic downturn and the wars in Iraq and Afghanistan.
Still, it was with the stroke of the pen that implemented immediate change on the president's first full day in office as Obama signed executive orders. He imposed new rules on government transparency, putting a pay freeze on senior staffers and mandating new limits on lobbyists.
"When you leave government, you will not be able to lobby my administration for as long as I am president. And there will be ban on gifts by lobbyists to anyone serving in the administration as well," said Obama.
U.C. Berkeley political science professor David Karol Ph.D., believes lobbyists will find a way to work around the new rules, but the new restrictions still send a clear message.
"On the first day this is the kind of thing you can do. You can set the tone about your administration," said Karol.
And on Thursday, the president will continue to set the tone. He will sign an executive order that will shut down the Guantanamo Bay prison within one year. Stanford law professor Jenny Martinez filed briefs for some of the detainees.
"It sends a clear message to the rest of the world that the U.S. is going to be a leader in human rights again, we're going to be the country that everyone admires and respects," said Martinez.
Also, the president will issue additional executive orders that would end harsh interrogations and require an immediate review of the more than 200 terror suspects held at the naval base.