HONOLULU -- A Maui judge Friday gave Hawaii Superferry permission -- with 24-hours notice -- to make a single voyage to Maui to return stranded passengers and vehicles to their home island.

Meanwhile, more legal concerns were added to the list for the Superferry.

The Superferry has been docked since protestors on Kaua`i blocked Nawiliwili Harbor, and a judge temporarily banned it from using Kahului harbor.

Friday, the state Supreme Court explained why the state and ferry must do an environmental assessment.

The court said the state wrongly concluded piers for the Superferry could be built without considering all of the Superferry's impacts.

Opponents said that means all those impacts must now be studied.

The Supreme Court did not say whether Superferry would be allowed to operate during the study.

That decision is left to the judge on Maui.