How it should look:
The last government official on Earth, a meter maid, vows to maintain law and order in a post-apocalyptic world.
Why it should look that way:
Earth, when it refers to the planet/world rather than dirt/land, should always be capitalized.
On the other hand, meter maid should not be capitalized.
Since law and order is a commonly used phrase, it’s highly probable that order is the word missing after law and.
(WordPress’ spellchecker wants me to replace maid with made. *shakes head*)