Of the 653,000 people who experience homelessness in the United States, 41 percent live in the nine westernmost states, according to the most recent federal survey. That includes the five states with the highest rates of unsheltered people. There are many reasons for this, from patterns of poverty and drug addiction to the benign weather in California — 68 percent of whose 181,000 homeless people were unsheltered, more than any other state. A little-known but crucial factor, however, is that all these states are under the jurisdiction of the U.S. Court of Appeals for the 9th Circuit, whose unique legal doctrine has effectively barred most enforcement of local public camping bans.