A Panama court dismissed a case by the Western Sahara Polisario independence movement to block a Moroccan shipment of phosphate in Panama saying there was no evidence the cargo belonged to the group, the Moroccan phosphate producer said on Thursday.

Polisario in May filed a claim to hold the Danish charter vessel Ultra Innovation, carrying 55,000 tonnes of phosphate rock from Morocco’s Office Cherifien de Phosphate (OCP), through Panama to the Port of Vancouver for the Canadian company Agrium.

The detention of the vessel was a new legal tactic by the independence movement in its conflict with Morocco over Western Sahara, a disputed territory where the two sides fought a war until a 1991 ceasefire.

“The court ruled that a domestic court is not the appropriate venue to consider purely political matters. It also ruled there is indeed no evidence demonstrating that the cargo on board belongs to the plaintiffs,” OCP said in a statement.

Panama court authorities were not immediately available for comment to confirm the OCP statement. Polisario said its lawyers were not aware of such a decision.

In late May, Panama judicial sources and Agrium said the shipping company posted a bond for the release of the ship.

By trying to seize Moroccan phosphate vessels, Polisario had tested a European court ruling last year that Western Sahara should not be considered part of the Moroccan kingdom in EU and Moroccan deals. Polisario said phosphate shipped from the disputed territory does not belong to Morocco.

Western Sahara has been disputed since 1975, when Morocco claimed it as part of the kingdom and the Polisario fought a guerrilla war for the Sahrawi people’s independence. A 1991 ceasefire split the region in two between what Morocco calls its southern provinces and an area controlled by Polisario.

Morocco’s OCP is the world’s leading phosphate exporter and operates in the Moroccan-held areas.

U.N.-backed negotiations have failed for years to end the dispute. Morocco wants the region to have autonomy within Moroccan sovereignty. Polisario wants to hold a referendum on self-determination, including on the question of independence.