Eighty-eight-year-old retired metallurgist Bob Wallace is a self-described tinkerer, but he hardly thinks of himself as the Thomas Edison of the illegal drug world. He has nothing to hide. His product is packaged by hand in a cluttered Saratoga garage. It's stored in a garden shed in the backyard. The whole operation is guarded by an aged, congenial dog named Buddy. But federal and state drug enforcement agents are coming down hard on Wallace's humble homemade solution he concocted to help backpackers purify water. Wallace says federal and state agents have effectively put him out of business, because authorities won't...