A federal jury in June convicted Walt Staton of littering in the Buenos Aires National Wildlife Refuge.
In August, a judge ordered Staton to pick up trash for 300 hours and also sentenced him to a year of unsupervised probation and banned him from the refuge for a year.
Staton is a member of the group No More Deaths, which supports humanitarian aid along the border.
He was scheduled to be re-sentenced Friday after he told the U.S. magistrate last month that he objected to the court's punishment on moral and legal grounds.
But Magistrate Jennifer Guerin denied Staton's motion to modify or suspend his sentence pending appeal and threatened to double his community service hours to 600 hours or give him 25 days in prison.
Guerin has scheduled a probation violation hearing for Dec. 21.
On the Web
No More Deaths: http://www.nomoredeaths.org/