A federal judge on Thursday said that activists with Greenpeace USA who are staging a blockade of an Arctic drilling support vessel are in contempt of a court injunction, and issued the organization a $2,500 hourly fine.

In an effort to prevent Shell from starting its offshore drilling operation in the Alaskan Arctic, thirteen activists with the group suspended from the St. Johns Bridge in Portland, Ore. for over 30 hours starting Wednesday morning, successfully forcing the vessel, the MVS Fennica, to make a dramatic u-turn on Thursday.

Their efforts have been buoyed by a coalition of “kayaktivists” who have repeatedly taken to the water to stage paddling blockades.

But attorneys for the energy giant said that the group staging a direct action at the bridge should be fined because it is violating a court ordered “buffer zone” preventing such actions.

U.S. District Court Judge Sharon Gleason agreed, stating (pdf) in her order: “Greenpeace, Inc. will remain in civil contempt so long as its activists continue to hang from the St. Johns Bridge in Portland, Oregon with the Fennica located upstream of that bridge.”

The fine is set to increase daily if the protesters continue the action—on July 31 the sanction becomes $5,000 an hour, on Aug. 1 $7,500 an hour, and on Aug. 2 $10,000 an hour.