WASHINGTON  A federal district judge on Monday blocked President Obama’s 2009 executive order that expanded embryonic stem cell research, saying it violated a ban on federal money being used to destroy embryos.

The ruling came as a shock to scientists at the National Institutes of Health and at universities across the country, which had viewed the Obama administration’s new policy and the grants provided under it as settled law. Scientists scrambled Monday evening to assess the ruling’s immediate impact on their work.

“I have had to tell everyone in my lab that when they feed their cells tomorrow morning, they better use media that has not been funded by the federal government,” said Dr. George Q. Daley, director of the stem cell transplantation program at Children’s Hospital Boston, referring to food given to cells. “This ruling means an immediate disruption of dozens of labs doing this work since the Obama administration made its order.”

In his ruling, Chief Judge Royce C. Lamberth of Federal District Court for the District of Columbia wrote that his temporary injunction returned federal policy to the “status quo,” but few officials, scientists or lawyers in the case were sure Monday night what that meant.