There is now a permit process to help landowners pursue clearing on adjacent land owned by the Bureau of Land Management (a federal agency). Thanks to the advocacy of Bob Long, chair of the Sherwood Forest Firewise Community, BLM (which has a large piece of land on the back side of numerous Sherwood Forest homeowners' properties) created this Defensible Space Permit Application which you can download here. Their phone number is not on the application; it's (916) 941-3101.
Should BLM should do this work themselves? Sure, but they are greatly understaffed and underfunded. Contact your local Congressperson to ask for increased federal funding of BLM for fire safety.