Gary Gutting questions the bishops' authority:
It may be objected that, regardless of what individual Catholics think, the bishops in fact exercise effective control over the church. This is true in many respects, but only to the extent that members of the church accept their authority. Stalin’s alleged query about papal authority (“How many divisions does the Pope have?”) expresses more than just cynical realpolitik. The authority of the Catholic bishops is enforceable morally but not militarily or politically. It resides entirely in the fact that people freely accept it.
Earlier Dish on the contraception controversy here, here, here and here.