Security should need to follow laws

[Frank_Stein]

A Security Officer should try to choose the least severe yet appropriate punishment. For most instances, time in the Brig and confiscation of any contraband should suffice. However, if a traitor is a lethal and immediate threat to the crew, lethal force may apply.

This is a very vague statement which can be interpreted differently by many people. I understand that the admin team does not want to restrict players but Space Law should ideally help players understand what is expected of them, both by the admin team and by other players.

"Least severe yet appropriate punishment"
Personally I would change punishment to response, since as Sec your job isn't to catch the criminals, it's to keep the crew and station safe from them

And that is how I think you should interpret this. When reacting to an incident, ask yourself "In what way can I deescalate this situation with the least amount of force?"

Sometimes that's gradual increases in pressure. Take a look at the procedure suggestion

1) Assess the situation.
2) Declare your intention.
3) Only stun suspects who show signs of resisting.
4) Processing suspects should take place inside the brig or a security checkpoint.
5) Processed suspects should be brigged ASAP.
6) Brigged suspects must be watched closely.
7) Watch your fellow officers.

First and second steps are about deciding what you should do, and making it clear you're about to do it. Third is when force comes into play, and it defines why you would use it.

So if you're worried about when something like an execution should apply, consider why that much force would need to be applied. The target would have to had to display the ability and willingness to perform lethal harm to the crew or station, in such a way that detaining them would not be able to dissuade them. 

As someone whom Sec is arresting, you should expect them to respond to you with somewhat the same level of aggression you're showing them, and for any detainment and punishment to be proportional to the threat you'd pose if free.