The proposed change targets spam robocalls that hijack legitimate, in-service numbers. Carriers like Comcast, T-Mobile, AT&T and Verizon are working to deploy STIR/SHAKEN technology that labels calls from authentic numbers. But the FCC says many voice providers have held off on developing call blocking tools because it was unclear whether those tools were legal under FCC rules.

"By making it clear that such call blocking is allowed, the FCC will give voice service providers the legal certainty they need to block unwanted calls from the outset so that consumers never have to get them," Pai said. If adopted, this ruling could lead to new call blocking tools, like those used by third-party apps. The systems would include protections against blocking emergency calls, and consumers would be able to opt-out of call blocking if they wish.

Don't expect robocalls to disappear immediately. The FCC will consider the proposal at its June 6th meeting, and if approved, it's hard to say when this will go into effect.