If someone raided me(even if I was unaligned), that nation, and any other that joined in on its side would eat nukes till they agreed to replace any tech they looted/destroyed.
Everyone has the authority to demand reparations for an unprovoked attack, that authority is backed by the credibility and scope of your threat.
Even without an alliance or nukes, a small but prepared nation can make it unprofitable to continue the war. What matters is whether the raider is nearsighted enough to continue a war when covering the damage you caused in aid would be cheaper, and if the attacked nation knows how to play his hand right.