You know how awhile back, Megatron set up base on Earth unopposed in a story called 'All Hail Megatron'?

Optimus Prime is getting in on the act

John Barber: Transformers #50 is the biggest thing we’ve done. It’s called "All Hail Optimus," and Optimus Prime annexes planet Earth to become to become part of Cybertron’s Council of Worlds—he takes control of Earth to protect it from invasion. Meanwhile, Optimus has thousands of Cybertronian followers who view him as the “True Prime”—they see him as having a power above any elected office, above any “normal” being—and now Optimus is using the power they’ve handed to him. And he’s using it for good—at least as far as he sees it. Not everybody agrees with him.