This rule already applies in towny. Specifically, I am looking at the rule in towny that says "You may not destroy any sort of infrastructure (railways, bridges, or other forms of infrastructure that cannot be realistically expected to be claimed)." The only reason why this isn't in nations is that people will use this to get people banned. However, this is a huge loophole since peaceful towns can do whatever they want and retreat to their base if they are threatened. You can't siege them, you can't kill them in their claims, and you can't defend your entire infrastructure system. For instance, I made a transatlantic train recently. 3 hours total and 5 stacks of iron blocks were used to make this. Someone from a peaceful town destroyed everything with mere iron tools in a day and a half. Although this isn't allowed in towny, it's perfectly fine in nations. I'd be absolutely fine with this if I was allowed to retaliate in any way. I can't grief their base, I can't siege them, and I can't take away their valuables because they have none. If they die, they don't care, they just make more iron tools and get right back to it. Thus, my suggestion is that peaceful towns should not be able to grief in general since nothing can be done to stop them. However, non-peaceful towns should be allowed to destroy infrastructure since you actually have the option of stopping them.