Whether you use Gmail or Microsoft Outlook or something else, your emails may be stored in servers outside the U.S. and potentially out of reach for law enforcement.

It's a question courts are grappling with in a case involving the FBI and Google. The question is: Can the FBI use a warrant to force Google to hand over emails stored in a foreign country?

In February, a federal judge in Philadelphia said yes, but Google is refusing to comply with the FBI. This decision goes against a higher court ruling in New York last July that said Microsoft did not have to pass along emails stored in Ireland.

Christopher Yoo, a law professor at the University of Pennsylvania, said it can go one of two ways.

"Either the Philadelphia-based federal courts will come to the same conclusion as the New York-based federal court, in which case, we'll have a unanimous set of law and it'll be no trouble," Yoo said. "It's also possible that the Philadelphia based court will come to the opposite conclusion, in which case it's quite likely the Supreme Court will take the case and decide the issue itself."

Yoo said the "big question in this case is whether the U.S. laws protecting privacy of email can be enforced in foreign countries."

He said there's another factor that courts may consider before deciding on this case -- whether or not a ruling can be used against the U.S. as well. He explained that if the U.S. government decides it has the right to access emails in other countries just because a U.S. company is involved, then other countries can make the same argument for accessing emails in the U.S. if a company from their country is involved.

Google is appealing the case. On March 10, Apple, Microsoft, Amazon, and Cisco filed a brief supporting Google.