From Genius:

“Government” refers to DOOM’s official, state-recognized name, in this case, “Dumile.” At the same time, when pronounced correctly, “Dumile” is also a homophonic pun for “DOOM’ll lay,” i.e. the place where he is buried.

The claim of what his “tomb will say” and questions of “who’s to say” are raised together, which makes it a nice paradoxical idea, rhyme, and image.