A set of anti-robocall principles signed by 51 states attorneys general and 12 cell carriers—including Verizon, T-Mobile USA and AT&T—was released last week as part of a new and ongoing collaboration that, among other things, asks providers to locate the source of suspected illegal robocalls and terminate "the party's ability to originate, route, or terminate calls on its network."

But the effort may run into a few challenges given the fact that not all robocalls are created equal. A few, for instance, can be useful, something that anyone who has ever consented to a drug store placing an automated call once a prescription was ready to be picked up, might already know.

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"There are instances in which telemarketing calls are legal," said Holly Melton, a partner at Crowell & Moring. "If [providers] make a mistake, then they are potentially blocking automatically dialed or pre-recorded message calls that consumers have actually asked for and want to receive."

Examples of robocalls that typically fall under the "legal" category include calls made by charities, political calls and survey calls. Commercial entities can also deploy robocalls to mobile phones provided they have obtained prior expressed written consent from the consumer.

Still, mistakes do happen. Melton relayed the story of a former colleague whose client wound up on a call-blocking list despite the fact that the client had secured the consent of its customers to receive automated calls.

Similar incidents could potentially be triggered by a bad actor's use of call spoofing to disguise a robocall behind a randomly generated telephone number.

"If a number is randomly generated and it happens to be a number associated with a company that makes legal robocalls, then they are going to land on that hit list and they won't be able to reach customers," Melton said.

Kevin Rupy, a partner at Wiley Rein, indicated that so-called "false positives" are a big topic of concern. But while it can generally be difficult to distinguish robocalls from other traffic on a carrier's network, voice providers aren't approaching the problem from scratch.

The anti-robocall principles require providers to implement STIR/SHAKEN, a technical and procedural framework that would allow voice providers to assign outgoing calls a certificate that, according to the anti-robocall principals, "cannot be faked."

In addition to STIR/SHAKEN, Rupy said voice providers are also using advanced analytics solutions to identify the presence of robocallers. Factors to watch for include a high-volume of calls from a single number or calls that tend be of a very short duration.

"So there are ways that reasonable analytics can pretty accurately determine whether a call is legal or illegal," Rupy said.

Andrew Lustigman, a partner at Olshan, raised the question of whether or not the government could potentially get involved in establishing some kind of guidance or criteria for separating helpful robocalls from harmful ones.

While the issues presented by automated or prerecorded calls have been around a long time—Lustigman's first case on the subject was 10 years ago—the law may still be playing catch up in some regards.

"It's always difficult to regulate when technology changes so rapidly. And that's the biggest problem that I think is there," Lustigman said.