Byron York:

There was one particularly striking moment in President Obama’s widely panned Oval Office speech on the Gulf oil disaster. About midway through his talk, Obama acknowledged that he had approved new offshore drilling a few weeks before the Deepwater Horizon rig explosion on April 20. But Obama said he had done so only “under the assurance that it would be absolutely safe.”
Absolutely safe? Even before the Gulf spill, few defenders of offshore drilling would go that far. And when the president announced his drilling plan, on March 31, he said it was “not a decision that I’ve made lightly” and that he and his advisers had “looked at [it] closely for more than a year.” Surely he was told of the possible risks.
“If you can find anything that’s absolutely safe, I sure want to find out about it,” says Robert Bea, a professor of civil and environmental engineering at the University of California at Berkeley. “There is no engineering system that I am aware of that has zero likelihood of failure.”
“We can never be absolutely safe,” adds Ken Arnold, an independent consultant to the oil and gas industry. “The only way you can be absolutely certain of being absolutely safe is to shut down all production and all drilling from offshore today.”
So how did the president get the idea that new offshore drilling would be absolutely safe? Obama has often said he relies on a “green team” for advice on energy and environmental decisions. The top three members of the team are the director of the White House Office of Energy and Climate Change Policy, Carol Browner, Interior Secretary Ken Salazar and Energy Secretary Steven Chu. Did Browner, or Salazar or Chu assure the president that new offshore drilling would be “absolutely safe”?

The rest here. Short answer: Nobody will tell Byron who gave this information to the president.