The federal government’s courtroom war with Apple over iPhone encryption may be grabbing all the headlines, but a number of tech companies offer devices, apps, and messaging services with privacy settings that frustrate police investigations. And according to a new report, the Facebook-owned WhatsApp instant messaging app could be the next to face a legal challenge from the feds.

This is according to a NY Times story, which claims that WhatsApp — the world’s most popular instant messaging service — has been fighting law enforcement efforts to access users’ conversations.

Not that long ago, WhatsApp was one of many messaging apps that was light on encryption, meaning that even though messages were encrypted in transit, the folks at WhatsApp could still access that content if it chose to.

But the company has since added encryption that effectively locks out eavesdropping at any point in the transmission. Even if a court grants police wiretap order, this end-to-end encryption bars them from accessing users’ conversations.

And in fact, reports the Times, courts have been issuing these wiretap orders only to find out that the sought-after transmissions can not be decrypted.

This dispute is slightly different from Apple’s battle with the FBI. In that case, the court has ordered Apple to aid law enforcement in unlocking a terrorist’s iPhone; it’s not a matter of monitoring a text or voice conversation.

With WhatsApp, the issue issue is the government’s current inability to listen in on these transmissions or access any old conversations.

The question is: Should law enforcement officials be able to get a court to compel WhatsApp and other companies into weakening their encryption to comply with wiretap orders?

Yes, it would allow police to monitor conversations between suspects in a criminal investigation. But it would also leave open a door for hackers to listen in on any user’s WhatsApp chat.

The issue of app and messaging security may be a more controversial privacy question than the ongoing iPhone debate. After all, even if police are able to unlock a secure phone, the messages and other content on that device may still be locked down through means that have nothing to do with the phone’s operating system.

So why hasn’t the Justice Department made a huge legal stink about the WhatsApp encryption? Possibly because the government is waiting for a case like the Apple dispute, where a company’s failure to comply with a court order could be used against them in the public sphere.

Peter Eckersley from the Electronic Frontier Foundation tells the Times that the FBI and DOJ are “waiting for the case that makes the demand look reasonable.”

Even though Facebook and WhatsApp have yet to face serious legal consequences in the U.S., end-to-end encryption has landed the company in hot water elsewhere in the world.

Earlier this month, Brazilian authorities arrested Facebook exec Diego Dzodan after the company balked on complying with a court order to turn over WhatsApp-related information to police in a drug trafficking case. Dzodan has since been released.

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