Aides to Gov. Gavin Newsom of California say several people associated with the couple have been contacted by federal agents in the past week. He criticized the move as politically motivated.
In a letter to Interior Secretary Doug Burgum and national parks officials, several Democrats and a Senate independent said that members of the administration could face fines and even criminal prosecution.
With support from Markwayne Mullin and Robert F. Kennedy Jr., the kratom industry is pursuing a potentially lucrative policy. Mr. Mullin owns equity in a company that could benefit.