The Pentagon has authorised the temporary transfer of a military directed-energy system to the Department of Homeland Security (DHS) for testing and the development of tactics that could see it used against people attempting to cross the US-Mexico border illegally.
US Defence Secretary Pete Hegseth signed a memo in September approving a seven-month loan of one Active Denial System (ADS), commonly known as a “heat ray”, beginning that month, according to a document obtained by CNN.
The system will not be operated by Department of War personnel — the formal title of the US defence department since an executive order signed on September 5, 2025. DHS alone is responsible for its employment and for writing the relevant tactics, techniques and procedures.
At the end of the loan period, DHS may request further use for border operations.
The ADS projects an invisible beam of millimetre-wave electromagnetic energy (approximately 95 GHz) that is absorbed in the outermost fraction of a millimetre of skin.
Military descriptions state that this produces a rapid heating sensation comparable to opening a hot oven, generating an “instinctive and irresistible urge to run from the effect”. The US Marine Corps has said the tingling it causes can last up to 15 minutes.
The discomfort is intended to be temporary when exposure is brief.
Officials classify the weapon as non-lethal when used within design parameters, though past testing has recorded cases of blistering and second-degree burns under certain conditions. In trials conducted in 2007, eight of the more than 700 people exposed to the beam were burned and two required medical attention.
Range is reported as about 1,000 metres, a little more than half a mile, under suitable conditions.
Deploying the system at the border would be unprecedented.
Current and former Customs and Border Protection (CBP) officials have previously discussed its possible use for crowd dispersal in high-crossing areas, including around El Centro, in southern California, but it has never been fielded against migrants.
Proposals in 2018 were rejected by the then homeland security secretary Kirstjen Nielsen.
The system was briefly taken to Afghanistan around 2010 but was not used in combat. US officials also weighed deploying it against demonstrators in Washington DC during the unrest that followed the death of George Floyd in May 2020, CNN reported.
Internal concerns raised in earlier reviews included questions of effectiveness, use-of-force standards in a civilian law-enforcement setting, potential for direct or indirect injury (including people fleeing into water), and sovereignty issues if the beam affected individuals still on Mexican territory.
Homeland Security Secretary Markwayne Mullin, confirmed to the post in March 2026 and asked about the development, said the department is “always evaluating technology on the border” and that “deterrent is the best option we have”.
He added that DHS would use “whatever tool we have at our disposal” to prevent illegal entry and described the technology under consideration as less-lethal or non-lethal.
A CBP spokesperson stated that the agency continually evaluates new technologies that enhance operational effectiveness.
The authorisation arrives amid a broader administration focus on border enforcement.
DHS said on October 16 that the US Border Patrol recorded 98,708 apprehensions on the southwest border in the 2026 fiscal year, which closed on September 30 — the lowest annual total since 1968 and roughly 95 per cent below the levels registered under the previous administration.
Reporting has noted that encounters have fallen sharply in recent periods, prompting some former officials to question whether the system is necessary. Critics have raised ethical and legal objections to applying military crowd-control technology to civilian migration enforcement, while supporters frame it as a non-lethal option for deterrence.
European governments have turned to comparable equipment on their own external borders. Greek police have mounted long-range acoustic devices on armoured vehicles along the Evros river frontier with Turkey, firing bursts of sound at a volume that has been likened to a jet engine.
No testing location or operational plan has been publicly specified. The arrangement remains limited to evaluation and tactic development rather than confirmed deployment.
The Pentagon’s heat ray technology is officially being tested for deployment at the southern border.
Are you good with directed energy, or would you rather stick with classic water cannons? pic.twitter.com/lbSIVgY3EC
— Desiree (@DesireeAmerica4) October 24, 2026
