A South African court blocked Shell from using seismic waves to explore for oil and gas in the Indian Ocean on Tuesday.

A court decision handed a landmark victory to environmentalists worried about the impact on whales and other species against oil giant Shell.

The High Court in the Eastern Cape town of Makhanda backed a suit filed by conservationists and local groups.

Members of the court declared Shell was banned from “undertaking seismic survey operations”, a decision that had an immediate effect.

The fossil-fuel giant had planned to start exploration over more than 6,000 square kilometers of ocean off South Africa’s coast. The ecologically sensitive area known as the Wild Coast is dotted with a marine stretch that is home to nature reserves.

According to a judge, consultations with coastal communities had been “substantially flawed”, which made Shell’s survey application “unlawful and invalid”.

This decision marks the end of a legal battle that saw protests gathering thousands of demonstrators on beaches around the country.