The decision announced in the government gazette called the Federal Register on Wednesday does not prohibit export of these nuclear materials — that are used as radionuclides embedded in devices — altogether, but make it mandatory for exporters to seek government’s permission every time and for every specific consignment.

Radionuclides are radioactive elements used widely, among other fields, in medicine and for irradiation of food.

“The US Nuclear Regulatory Commission (NRC) is issuing an Order suspending the general license authority under NRC regulations for exports of byproduct material to Pakistan,” said the announcement in the register. “Exporters are no longer authorized to use the general license to export byproduct material to Pakistan and now must apply for a specific license pursuant to NRC regulations.”

It did not ascribe any specific reason other than that the Trump administration has determined that the suspension is “necessary to enhance the common defense and security of the United States and is consistent with the provisions of the Atomic Energy Act”.

The order did not say so, but under relevant rules, a country’s proliferation record can be ground for cancellation of export license.

“The Commission will closely monitor these countries and may at any time remove a country from a general license in response to significant adverse developments in the country involved,” says the code of federal regulations for the energy sector. “A key factor in this regard is the nonproliferation credentials of the importing country.”

A response was awaited from the US Nuclear Regulator Commission (NRC) to a request for the reasons for the suspension.

The announcement came after President Donald Trump and Pakistani Prime Minister Imran Khan talked on phone about the coronavirus pandemic. Trump mentioned the call at the daily briefing of the White House task force but gave no details. It would not be ascertained if the nuclear export development figured in their discussion.

Pakistan’s history of nuclear proliferation has been a major concern for the United States, as for the rest of the world. The nuclear black market established by AQ Khan, who built Pakistan’s nuclear bomb with stolen technology that he then passed on to Iran, Libya and North Korea, is thriving.

The Trump administration has continued to pursue Pakistani government agencies, private contractors and fronts, who have sought to find a way around US rules and conditions, with unmitigated urgency and unchanged priority.

The immediate trigger for Wednesday could not be ascertained. But Joshua White, a former top White House official for South Asia who first flagged the Federal Register announcement, said, “We can’t be certain what prompted this move by the NRC. It may have been undertaken in response to a series of technical violations or regulatory oversights, or it may be in response to broader US concerns related to Pakistan’s nuclear programs or non-proliferation commitments.”

The US justice department indicted five Pakistani and Pakistani-descent men in January for using front companies to procure American goods for Advanced Engineering Research Organization and the Pakistan Atomic Energy Commission, both Pakistani government agencies that are on the US “Entity List” of exporting destinations whose activities have been declared “contrary to US national security or foreign policy interests”.

In 2018, seven Pakistani organizations were added to the US “Entity List”, a US commerce department blacklist of governments, government agencies, private companies and individuals viewed as a threat to US national security and the export of sensitive US material to whom are tightly controlled and are subject to specific government clearance.

The Wisconsin Project on Nuclear Arms Control, a non-partisan, and non-profit body that seeks to end proliferation by tightening export control regimes in source countries such as the United States, said in a report in September 2019, that since 2014, the US commerce department has added 40 Pakistani or Pakistani-related entities to that list.