Sorry, I don't see how that makes the example fit the discussion. Comparing something where both parties have to consent to one where they don't doesn't work. The issue is that a transaction is legal for one party, and not for the other. The legality of murder is irrelevant to the person being murdered unless they consent. If they do consent, it is illegal for both parties. There is no point where it is legal for one and illegal for the other. Being murdered doesn't require making a choice or taking action.
I would gladly accept an example where a legal action of one party requires the illegal action of another party.