This was done before. Suggest you watch the documentary "Die Another Day". Some north korean launched it and when the Americans sent missiles to destroy it, he just aimed his mirror at the missiles and fried them.
The mirror was demoed at some ice castle in Iceland when he benevolently lit up just the castle at night to impress the guests, but then focused mirror to try to fry some british spy out to disable mirror.
Curiious which international body could stop this.