Leaders of the armed occupation of the Malheur National Wildlife Refuge last winter were found not guilty yesterday of conspiring to impede federal officials in a shocking loss for the government. "I don't know how this verdict can't serve to embolden people that they can be free to take actions that involve threats of violence and instructions on public lands and escape with impunity," said Bob Dreher, a former acting assistant attorney general for the Justice Department's environmental division. "It's a little scary."