“We cannot tolerate another case of Asian-Americans being wrongfully suspected of espionage,” Representative Judy Chu, Democrat of California, said last fall. “The profiling must end.”

While those cases raised the specter of Chinese espionage, none explicitly charged the scientists as spies. The cases involved routine criminal laws such as wire fraud, so national security prosecutors in Washington did not oversee the cases.

In a letter last month to federal prosecutors nationwide, Deputy Attorney General Sally Q. Yates said that would change. All cases affecting national security, even tangentially, now require coordination and oversight in Washington. That had always been the intention of the rule, but Ms. Yates made it explicit.

“The term ‘national security issue’ is meant to be a broad one,” she wrote.

Ms. Yates told federal prosecutors that consulting with experienced national security prosecutors in Washington would help “ensure prompt, consistent and effective responses” to national security cases.

The letter, which was not made public, was provided to The New York Times by a government official.

John P. Carlin, the Justice Department’s top national security prosecutor, reorganized his staff in Washington in recent years to focus more aggressively on preventing theft of America’s trade secrets. The new rules mean that espionage experts will review cases like Dr. Xi’s. Such cases “shall be instituted and conducted under the supervision” of Mr. Carlin or other top officials, the rules say.