Followup to this question: Legality of "counter-blackmailing" with calling/reporting to the police

In it, an answerer provided two criteria for when blackmail is legal in the England and Wales jurisdiction:

(1)A person is guilty of blackmail if, with a view to gain for himself or another or with intent to cause loss to another, he makes any unwarranted demand with menaces; and for this purpose a demand with menaces is unwarranted unless the person making it does so in the belief—

(a)that he has reasonable grounds for making the demand; and

(b)that the use of the menaces is a proper means of reinforcing the demand.

I am now applying this to the more general act of extortion. I find proper means to be a bit vague here. Take the following scenario;

In my country (Norway), it is illegal to cut power to someone who isn't paying their electrical bills if a resident is a minor.

In a minor-free residence, a company making the threat "if you don't pay up, we will cut your power", satisfies (a) and (b). However, if they make the same threat to a residence that houses a minor, (a) is still satisfied. As for (b), I am not quite sure; is threatening to do something illegal an "improper" way of inforcing the demand? It wouldn't surprise me, but I interpreted "proper" more to mean, "the thing you're threatening to do is the best way of maximizing the likelihood that you get what you want". If this interpretation is correct, then it would be improper for the company to orally deliver the threat to a resident that is blind, deaf and at the moment of deliverance, without other people to relay the message. It is improper, because the use of the menaces weren't the best way; heck, not a way at all; to inforce the demand.

However, maybe legality is a criterium for the use of menaces to be proper? A threat requires there to be the promise of a harm or loss to a person or their property. However, when the person fail to pay the electrical bills, the electricity running to their house is no longer their property. So, when the company says they'll cut the power to this minor-housing residence, they aren't threatening them (since they don't own the electricity anymore), but they are saying that they'll do something illegal. Does the fact that the act of which they're saying they'll do is illegal, make their speech constitute threats, and thus their act constitute extortion?