In October 2017, Ben Cassidy walked away from his lucrative lobbying gig at the National Rifle Association, where he raked in as much as $288,333 per year , for a post at the Department of the Interior. Hed spent nearly seven years trying to reshape the agency as part of the gun lobby, and despite seemingly clear ethics rules against it , he was soon working on national monuments, sport-hunted animal trophy imports and other issues hed lobbied on.

In July, less than three months after his conduct became the subject of a formal department ethics probe , Cassidy quietly left his position as the Interior Departments senior deputy director of intergovernmental and external affairs to join Safari Club International. The Washington, D.C.-based trophy hunting advocacy group has close ties to the Trump administration and is one of several organizations that successfully lobbied the Interior Department to roll back prohibitions on importing lions and elephants killed for sport in certain African countries.

Cassidy is a prime example of the revolving door at President Donald Trumps Interior Department. A HuffPost review found that at least 11 former officials have landed jobs in industry or lobbying since leaving the federal agency.

Three of them Cassidy, Vincent DeVito and Todd Wynn departed not long after getting wrapped up in a formal investigation by the agencys Office of Inspector General. That probe targets six current and former officials who maintained close ties to former employers, and stems from a complaint the D.C.-based nonprofit Campaign Legal Center filed with the Interior Departments internal watchdog that cites HuffPosts reporting and alleges a disturbing pattern of misconduct across the agency.

Trump campaigned on a promise to drain the swamp of lobbyists in Washington and signed an executive order shortly after taking office that requires all political appointees in the executive branch to sign an ethics pledge. Along with barring former lobbyists from participating in matters on which they lobbied, it includes post-employment restrictions that prohibit political appointees from lobbying their former agencies for five years after leaving government service. Federal ethics rules also include a so-called cooling off period preventing senior executive branch officials from lobbying their former agencies for one year.

Trumps ethics pledge is not as clear as it may seem. Virginia Canter, chief ethics counsel at the Washington-based government watchdog Citizens for Responsibility and Ethics, or CREW, says theres a big loophole that allows lobbying on rulemaking the very thing that agencies like Interior Department do and that groups like Safari Club want to influence.

The language, Canter said, completely takes the teeth out of employment restrictions for recent government employees. More than 30 former Trump officials have managed to skirt the pledges lobbying prohibitions using this and other loopholes, according to a February report by ProPublica.

If you can imagine a target, this thing is shot full of holes, Canter said of the administrations pledge.

Delaney Marsco, ethics counsel at the Campaign Legal Center, told HuffPost that even if these officials arent breaking those rules, their activity is emblematic of the bigger revolving door problem in Washington, in which industry insiders serve short stints in government, only to return to work for the companies they previously regulated.

The conduct of these Interior officials, both in office and after, raises serious questions about whether those officials used their time in government to serve the publics interests or the interests of the wealthy, influential industry groups who could line their pockets, she said.

Here are some of the key officials who have dashed through the revolving door at Trumps Interior Department: