Eddie Leroy Anderson of Craigmont, Idaho, is a retired logger, a former science teacher and now a federal criminal thanks to his arrowhead-collecting hobby.

In 2009, Mr. Anderson loaned his son some tools to dig for arrowheads near a favorite campground of theirs. Unfortunately, they were on federal land. Authorities "notified me to get a lawyer and a damn good one," Mr. Anderson recalls.

There...