Cooperating with a government investigation sounds like a good idea, but it can cost companies quite a bit of money.

A recent decision by the Supreme Court, in Lagos v. United States, will make life more difficult for corporations hoping to recoup some of those costs from employees who violated the law.

The Justice Department puts a premium on corporate cooperation. Its “Principles of Federal Prosecution of Business Organizations” assert that “for a company to receive any consideration for cooperation under this section, the company must identify all individuals involved in or responsible for the misconduct.” Rod J. Rosenstein, the deputy attorney general, reiterated the point in a speech last month, saying that “corporate America should regard law enforcement as an ally.”

That ally doesn’t come cheap, however.

The Lagos case concerned a provision of the Mandatory Victims Restitution Act, which required a defendant to reimburse a victim for “lost income and necessary child care, transportation and other expenses incurred during participation in the investigation or prosecution of the offense or attendance at proceedings related to the offense.” Sergio Fernando Lagos was convicted of defrauding General Electric Capital out of millions of dollars by submitting false invoices to draw down loans. The District Court ordered him to repay the company about $5 million in legal and accounting fees it incurred conducting an internal investigation into the fraud and dealing with his company’s bankruptcy.