A federal judge dealt another setback to the J.R. Simplot Co. and other ranchers by reaffirming his late-February decision to halt grazing on 17 Bureau of Land Management allotments covering some 450,000 acres in southern Idaho.  Wednesday's ruling by U.S. District Judge B. Lynn Winmill also ordered that cattle be removed from the allotments by May 3.   Western Watersheds Project director Jon Marvel said Winmill's decision will protect thousands of acres of critical sage grouse habitat from livestock grazing.  Marvel's group aims to shut down grazing on public land in the West.  This decision is the latest development in Western Watersheds' 2005 lawsuit contending the BLM violated federal law by authorizing grazing in the midst of southern Idaho's sage grouse country that's been hard hit by wildfire in recent years.