Harry sighed. "There might come a time when you have to," he said calmly. "when he summons you to protect the school, and he's the headmaster, in all likelihood one day he will have to summon the Order to do just that, we need to know that you'll respond to that too," he said.
"Anyway, while Dumbledore is still around, it's a moot point, but it's something you have to consider."