A top official in the Trump administration resigned this week after being told by the White House that he would not receive a permanent security clearance after he admitted to prior drug use.

George David Banks, who served as special assistant to the president for international energy and environmental policy, resigned from his position on Tuesday after admitting to smoking marijuana in 2013. Politico reports:

A former CIA analyst who also previously worked at the State Department and the White House Council on Environmental Quality, Banks emerged last year as the administration’s lead policy expert on the Paris climate change agreement, and he played a key behind-the-scenes role in the months-long internal debate over whether to remain in the pact.

A former Obama administration official who worked on personnel and vetting issues said the Obama White House usually only denied clearances when there was both past drug use and a lack of full disclosure.

Banks was among the nearly three dozen other White House officials operating on an interim security clearance while the administration evaluated the status of their permanent security clearance application.

When Banks was informed that he did not qualify for a permanent security clearance, he offered his resignation to the White House, which they accepted.

“It was an honor to serve the president at the White House and I look forward to supporting the president in the future,” Banks said.

Politico reports that the Trump administration has cracked down on the use of temporary security clearances in the last few months, imposing “a ban on new interim security clearances for anyone in the executive office of the president last fall, but let existing employees with interim clearances stay on.”