The Westerschelde is that part of the Scheldt river between Antwerp and the sea, passing between Zeeuws-Vlaanderen to the south and the islands of Zuid-Beveland and Walcheren to the north.

For almost twenty years now, the Antwerp port authorities, together with the companies who operate out of the harbour, have pressed for a deepening of the Westerschelde channel at 12 important points. Otherwise, they warn, the port will lose the custom of the larger container ships, as they are unable to navigate the channel and travel as far as Antwerp except at certain tide-times, which restricts access severely.

The problem is, the chief beneficiary of that development would be Antwerp's main competitor Rotterdam. At the same time, the greater part of the Westerschelde is in Dutch territory: the Belgian part extends only as far as the border about 8.5km north of Lillo. That work has been done, but it doesn't tackle the main problem. The Dutch, however, have little incentive to deepen the Westerschelde. There's little economic benefit for them, and the works would cause problems on their own territory, with some farms losing land through ontpoldering: as water levels rise, some of the land previously reclaimed from the Scheldt would be taken back.

After much discussion, the two sides reached a treaty agreement in 2005 by which the works would be carried out. But the Dutch continued dragging their feet. In his government statement following the election in June, in which he set out his priorities for the new administration, Flanders' minister-president Kris Peeters mentioned the Westerschelde work as one area where progress would need to be made.

The Council of State has made that virtually impossible. Two nature organisations, the Zeeland Environment Federation and the Birds Protection agency, brought a motion to suspend the treaty, arguing that nature preservation areas would be adversely affected by the works. The Council issued an interim suspension of the treaty, which seems likely to become permanent later in the year when the final ruling is handed down.

Antwerp, in the person of port affairs alderman Marc Van Peel, reacted furiously, blaming the Dutch government for failing to meet its treaty obligations, and for creating the latest situation. The government of Jan Peter Balkenende suddenly switched track in April from a plan which involved selective ontpoldering to one in which would have involved laying down estuarine marches outside the sea-dykes along the Westerschelde, raised areas which would provide feeding and roosting terrain for birds which would partially flood at high water. But the nature groups argued that the government's nature provisions were uncertain and vague. The Council of State agreed.

Rudy de Meyer, director of Alfaport, the association of port employers, called the Dutch position "unacceptable," arguing that the change from ontpoldering was directly responsible for last week's decision. Kris Peeters, meanwhile, called on his Dutch counterparts to make it an immediate priority to put the Westerschelde treaty into operation in its entirety, including the nature-protection aspects.