A federal appeals court in San Francisco has tossed out the conviction of an Arizona man who left water jugs in the desert for migrants passing through.

Two years ago during a bench trial, a U.S. Magistrate in Tucson found Daniel Millis guilty of littering.

Millis and the faith-based aid group No More Deaths had regularly helped migrants by offering them food, water and medical aid. Prosecutors said Millis was leaving behind garbage and failing to follow orders by federal agents to remove it.

In reversing the conviction, the appeals court said the term "garbage" is "sufficiently ambiguous" and should be resolved in favor of the defendant.