South Butte and the entire surrounding Sutter Buttes range is private property and trespassing is illegal. The land is actively monitored with cameras, motion sensors, and other surveillance. If you are caught trespassing, you will be arrested and could be subject to jail time and steep fines. DO NOT illegally trespass on this land!!
Legal access is possible by joining a guided trip, arranged by hiking club members and the local land manager. Coby King (cobyk [at] cobyking.com) of the Sierra Club is currently the point person to contact about future trips.
Please do not "stealth" this high point, since it puts the arranged legal visits in jeopardy.