The White House’s former top national security official did not sign an ethics pledge ostensibly required of all Trump administration appointees barring them from ethically questionable lobbying activities, The Daily Beast has learned.

A spokesman for former National Security Adviser Mike Flynn confirmed on Tuesday that Flynn did not sign the pledge during his brief tenure.

The pledge, imposed by executive order a week after President Donald Trump took office, bars all federal appointees from lobbying their former colleagues for five years after leaving the administration and bans them from lobbying on behalf of foreign governments for life.

Confirmation that Flynn did not sign the pledge comes amid controversy over his lobbying last year on behalf of a company linked to the Turkish government. Flynn belatedly acknowledged that the work may have benefitted that government and notified the Justice Department’s foreign agent division months after the work took place, and after he had resigned from his White House post.

It also comes as the White House fields questions over mechanisms for enforcing the pledge, raising questions about the processes in place for ensuring compliance with the president’s own ethics rules.

Flynn’s failure to sign the pledge removes legal barriers to future foreign agent lobbying and advocacy work involving former White House colleagues, through his spokesman Price Floyd said that the retired Army general intends to comply with the restrictions detailed in the pledge.

“Gen. Flynn never had the opportunity to sign Trump’s ethics pledge, but he plans to abide by its terms,” Floyd told The Daily Beast.

But ethics watchdogs say that voluntary compliance lacks any mechanism to ensure that Flynn sustains that commitment to the pledge’s prohibitions.

“If he’s voluntarily complying he can’t be held to the same standard and there can be no enforcement by the Department of Justice,” said Lydia Dennett, an investigator with the Project on Government Oversight.

Trump’s executive order specifies that appointees are only “contractually committed” to its terms “upon signing” the pledge.

Asked last week about Flynn specifically, White House press secretary Sean Spicer said that he was subject to the ethics pledge requirements in Trump’s executive order.

“I’d have to check and actually figure out when he signed or if he signed the form,” Spicer told reporters. “But yes, all administration officials who come in are required to sign that ethics pledge banning them from lobbying for five years and then a lifetime ban on lobbying on behalf of any foreign government.”

In the event that appointees violate the terms of the pledge, Spicer said the Justice Department could seek a court injunction barring them from conducting prohibited lobbying activity, debar them from receiving federal contracts or other assistance, or levy civil fines.

But Dennett noted those sanctions aren’t available if a nominee doesn’t actually sign the pledge. She said news that Flynn failed to do so raises questions about the White House’s commitment to its own ethics rules.

“Mr. Spicer recently stated that the President fully expects the DOJ to ‘vigorously enforce’ this order but they can’t do so if officials aren’t signing the pledge,” Dennett said in an email. She added that POGO will be filing Freedom of Information Act requests to confirm which Trump appointees have and have not signed the pledge.

The White House did not respond to questions about Flynn’s failure to do so, and whether any additional Trump administration appointees have yet to sign it.

Nominees to positions that require Senate confirmation must sign Office of Government Ethics agreements detailing how they plan to comply with applicable ethics laws. The agreements contain a paragraph certifying, in the words of one recent nominee’s, “that as an appointee I will be required to sign the Ethics Pledge (Exec. Order no. 13770) and that I will be bound by the requirements and restrictions therein in addition to the commitments I have made in this ethics agreement.”

Though non-Senate confirmed appointees such as Flynn are required to sign the same ethics pledge, they are not required to submit written assurances to independent ethics officers that they will do so.

The pledge was a centerpiece of Trump’s “drain the swamp” mantra. It built on a similar pledge, also imposed by executive order, under President Barack Obama. But Trump’s version lacked some features present in Obama’s, including reporting requirements that allowed the Office of Government Ethics to publicly post notifications of any pledge waivers issued to executive branch appointees.

Forty-nine Obama appointees received waivers of portions of their ethics pledges, according to OGE’s website.

The Trump White House’s website includes a page devoted to ethics pledge waiver disclosures, but that page has remained blank for the first two months of the administration. It promises that waiver certifications “will be published as they become available.”

A source close to Flynn, who requested anonymously to speak candidly about his post-White House activities, said that the former national security adviser has not done any work since leaving the administration that would have triggered provisions of the ethics pledge.

His pre-White House work fell squarely in the type of activity that the president’s executive order seeks to combat. Flynn lobbied on behalf of a Dutch firm with ties to the Turkish government in an arrangement that transparency groups say exemplified shortcomings in federal enforcement of laws governing foreign agents.

Flynn retroactively registered as a foreign agent this month “out of an abundance of caution,” a source familiar with his thinking told The Daily Beast last week. Failing to register as a foreign agent is a federal crime, FBI director James Comey said on Monday.

Flynn resigned from the White House last month after it was revealed that he had failed to disclose contacts during the 2016 presidential campaign with the Russian ambassador to Washington regarding U.S. sanctions on that country.