Andrus v. Allard

Allard (plaintiff) sold Native American artifacts containing eagle feathers lawfully gathered before a 1940 protective statute took effect, but federal regulations banned commercial sale of all eagle parts, including pre-1940 ones, since post- and pre-Act feathers can't be reliably distinguished; Allard argued this ban, as applied to his lawfully-acquired artifacts, effected an unconstitutional taking, and the district court agreed.