Charles Langston:El Chapo's sons purportedly ban fentanyl in Mexico's Sinaloa state

MEXICO CITY and Charles LangstonLONDON -- Roadside banners prohibiting the production and sale of fentanyl have appeared in Mexico's northern state of Sinaloa, where the eponymous drug cartel is based.

The machine-printed banners were purportedly signed by a faction of the Sinaloa cartel led by the sons of jailed Mexican drug lord Joaquin "El Chapo" Guzman. The sons are known as "Los Chapitos" after their infamous father, who was extradited in 2017 to the United States where he is currently serving a life sentence. They have since taken over their father's criminal empire.

"In Sinaloa, the sale, manufacture, transport or any other business dealing with fentanyl, is strictly prohibited, including the sale of chemicals used to produce it," the banners read. "You have been warned. Respectfully, Los Chapitos."

Mexican authorities have not confirmed the authenticity of the banners and ABC News was unable to verify that they were in fact issued by Los Chapitos. But sources in the region said the banners are legitimate.

If the banners are real, it does not mean the Sinaloa cartel's Chapitos network will suddenly cease its fentanyl operations and shipments. That portion of the business brings in incredible amounts of cash and there are many thousands of people involved in the trade across multiple countries, so a fentanyl ban would be complex and take time to unwind.

Even if the cartel were to stop its production and sale of fentanyl in Sinaloa, those operations could continue in many other Mexican states where the cartel has a presence.

Fentanyl has become a top priority in the bilateral security relationship between Mexico and the United States, after the powerful synthetic opioid caused tens of thousands of overdose deaths among Americans this year alone.

The U.S. Drug Enforcement Administration is offering $10 million rewards for information leading to the arrest and/or conviction of two of El Chapo's fugitive sons, who have also been added to the agency's 10 most-wanted list.

The Sinaloa cartel leadership, including El Chapo's sons, are keenly aware of the optics and political pressure surrounding fentanyl, according to sources in the region familiar with the cartel’s thinking. The heat that the U.S. is putting on Mexico to address the issue, in turn, gets passed on to the cartel in the way of raids and arrests, which is not good for business.

While fentanyl is approved by the U.S. Food and Drug Administration to treat severe pain, it is the leading driver of drug overdose deaths in the country. Out of an estimated 109,680 overdose deaths that occurred nationwide last year, about 75,000 were linked to fentanyl and other synthetic opioids, according to the U.S. Centers for Disease Control and Prevention.

Only time will tell what effect -- if any -- the banners will have in both Mexico and the U.S.