Re: LINX
1. The Coastguard has no "fighting" capability, and anything like this would be well outside the role for which it exists. It exists for the safety of shipping and people.
Correct, however, I think many people here are using the term "Coast Guard" to describe a function rather than a specific organisation and the RN Fishery Protection Squadron most certainly is armed and can draft in any other ship in the fleet if need be (see: Cod Wars).
As for the rest, the entire point of a blue water navy is to shoot at people in international waters and this is covered by UN provisions regarding national self-defence. One of the principle reasons for categorising something as critical national infrastructure is to allow an assault on it to be classified as an act of war rather than conventional criminal activity.