If it happens repeatedly, declare the passage of all Russian ships (or possibly starting with ships of the type involved in the incident, allowing other shipping and giving Russia a chance to stop abusing it) "prejudicial to the peace, good order or security of the coastal State" and deny passage through territorial waters. Extend the territorial waters between Finland and Estonia to the full 12 miles without the current corridor in between.
Russia understands and responds to strength better than to diplomacy and appeasement.
The ships involved aren't warships. They're ostensibly civilian vessels. Also other people mention that accidental fiber cuts happen all the time. Are we going to drone strike Russian civilian ships on the off chance is malicious?
>Russia understands and responds to strength better than to diplomacy and appeasement.
The best way to stop someone committing war crimes is... to commit war crimes ourselves?
That has hardly stopped people before.
https://en.wikipedia.org/wiki/Sinking_of_the_Rainbow_Warrior
>The sinking was a cause of embarrassment to France and President François Mitterrand. They initially denied responsibility, but two French agents were captured by New Zealand Police and charged with arson, conspiracy to commit arson, willful damage, and murder.
There's unlikely to be anywhere near as much outcry if Russian trawlers lurking around undersea cables start getting holes in them.