BLM spokesman Larry Crutchfield said Wednesday he could not say whether the departure is related to the 13 felony charges Smart faces in a child sex-abuse case.
"It is our policy not to comment on personnel issues," Crutchfield said.
Smart, 60, faces two sodomy counts, six forcible-sexual-abuse counts, two kidnapping counts and a rape charge, all first-degree felonies. He also is accused of two second-degree felony counts of forcible sexual abuse.
According to court documents, the crimes took place at Smart's Kanab home between May and June 2005 when the female victim was 9 years old. A separate incident allegedly occurred near the Kaneplex rodeo grounds Sept. 9, 2006, when the same girl was 10.
Smart, who was on administrative leave from his BLM post, is free on $125,000 bond.
The veteran BLM official came under fire from off-road enthusiasts in August 2005 after ordering emergency restrictions on popular OHV trails. He also drew flak for trail closures and other limits spelled out in a recently proposed resource-management plan (RMP).
Crutchfield said the current review of that plan will not be affected by Smart's exit.
"The final decision on all the ongoing RMPs statewide rests with the [BLM's] state director," Crutchfield said.