Ah found it .....(MARITIME LAW......
The United Nations Convention on the Law of the Sea of 1982)
Suez canal
In terms of commercial navigation and traffic density the Suez Canal is the most important canal in the world.
Regulations for the Suez Canal were established in 1888 by the Convention of Constantinople. This was the first treaty in the history of international maritime law to grant free passage within a canal. Article 1 prohibits interference with vessels in the canal and so guarantees free passage in peacetime and war. Article 2 prohibits obstruction and interference with the security of the canal and its branches.