The five-member Supreme Court ruled last week that the state had to conduct an environmental review of the ferry service, in a move that resulted in the suspension of the Superferry's Honolulu to Kahului service.

Today, the high court issued a 104-page opinion explaining the rationale behind its decision.

"Stated simply, the record in this case shows that DOT did not consider whether its facilitation of the Hawaii Superferry Project will probably have minimal or no significant impacts, both primary and secondary, on the environment," wrote Associate Justice James Duffy, who authored the opinion.

Duffy's conclusions echoed arguments by local environmental groups including the Sierra Club, Maui Tomorrow and the Kahului Harbor Coalition, which sued the state in 2005 over its handling of the Superferry.

Isaac Hall, attorney for the three environmental groups, said the environmental assessment required by the Supreme Court could take months to complete.

If the assessment indicates more study is needed, the state may have to conduct a full environmental impact statement on the Superferry. An EIS could delay the Superferry for up to a year.

Hawaii Superferry officials did not respond to calls seeking comment today.

Department of Transportation officials also had no comment and Deputy Attorney General Bill Wynhoff, who is argued the case on behalf of the DOT, did not return calls.

The opinion pertaining to Sierra Club vs. state Department of Transportation is available for viewing on the Judiciary's Web site.