Wanted to check. Obviously it was a powerful chokepoint to control.
simply block usage by a particular entity
I was fuzzy on the details so I did a bit of, very quick, digging. It seems that I had remembered the British as explicitly forbidding the Russians from transiting the canal when in truth it was more of an unstated threat that Britain used to discourage the main fleet from trying its luck in passing the canal. Legally, the canal was neutral waters and Russia had every right to pass through it, if it chose to. However Britain, having de facto control of the canal, had the flexibility to interpret the rules more or less as it wanted and so could potentially use or invent a pretext to delay the fleet's passage, prevent it from using the canal, or detain the fleet outright. Russia didn't feel confident in being able to pressure Britain in adopting a favorable position, especially with the all-important 2nd Squadron. However, when the 3rd Squadron came around the British had cooled down a bit, and the Russians, ultimately could afford to lose the 3rd Squadron if was prevented from passaing the canal. That made the chance worth it, and in the event Britain did not do anything to hinder the Russian force using the canal.It is adequate any time they blocked usage by a particular entity.
Thanks for the providing the example.
How did they implement this decision?
Declaring it was closed to Russia for the duration in advance?