DENVER — Opponents of the artist Christo's plan to suspend giant fabric panels over parts of the scenic Arkansas River are asking a federal judge to block him.

The group Rags Over the River contends the U.S. Bureau of Land Management violated federal environmental laws when it issued a decision last year allowing Christo's "Over the River" project. Christo hopes to start construction this year.

University of Denver student lawyers filed a lawsuit Wednesday on the group's behalf seeking to block him.

A BLM spokeswoman didn't immediately return a phone message seeking comment. Christo's team has said the BLM's approval included dozens of measures to mitigate impacts on traffic, safety and wildlife.

Some local approvals are still needed. Fremont County was holding public hearings Wednesday and Thursday on Christo's permit request there.