Nine out of 12 members of the National Park System Advisory Board on Tuesday quit out of “frustration” after Interior Secretary Ryan Zinke refused to meet with them, the Washington Post reports.

In a letter to Zinke, former Alaska governor Tony Knowles said the board members “have stood by waiting for the chance to meet and continue the partnership,” slamming the interior secretary for ignoring their “requests to engage.”

“We understand the complexity of transition but our requests to engage have been ignored and the matters on which we wanted to brief the new Department team are clearly not part of its agenda,” Knowles wrote. “I wish the National Park System and Service well and will always be dedicated to their success.”

Knowles told the Washington Post the board members “were frozen out” of recent Interior Department decisions to raise entrance fees and reverse a decision to ban plastic water bottles from the national park system.