Costa Rica and Nicaragua have been ordered to stay out of the disputed area on the Isla Calero until the International Court of Justice decides the situation on its merits.
In addition, Nicaragua may continue the dredging it has undertaken in the Río San Juan.
These were the core decisions ordered Tuesday by the court which is based in The Hague, Netherlands.
Costa Rica was given limited rights to send civilian workers into the disputed and sensitive territory for purposes of safeguarding the environment after giving notice to Nicaragua.
Costa Rica got less than it had hoped in the decision, which was read aloud in a 40-minute session. The reading was carried live in Costa Rica on Channel 6, and the court provided streaming video of the event.
The decision urged both countries to work together to resolve the situation, particularly as to
environmental damage. Each country must refrain
from aggravating the situation, said the decision.
A final rule may take years and these initial measures, which had been sought by Costa Rica, do not pre-judge the final verdict, said the ruling.
Nicaragua invaded the territory in October and later said it did so, in part, to fight drug trafficking. The court ordered both countries to keep an eye on criminal activity in the disputed area even though police and soldiers cannot enter.
The ruling said that the court could not conclude at this time that the dredging by Nicaragua would create irreparable harm in the area. Costa Rica sought an end to the dredging.
Nicaragua has constructed a channel that will become a new mouth of the Río San Juan, and Costa Rica had claimed this would cause irreparable damage to the existing waterways.
But the court did not agree.
The decision came at 8 a.m. Costa Rica time, which was mid-afternoon in The Netherlands.