Symbolism, Imagery, Allegory
Almost every time that Grant goes into any sort of official institution, like a school, church, or courthouse, he takes note of the flags that are flying outside. Check it out:
We pledged allegiance to the flag. The flag hung limp from a ten-foot bamboo pole in the corner of the white picket fence that surrounded the church. (5.1)
The boy raised his hand to his chest.
"Plege legen toda flag. Ninety state. 'Merica. Er—er—yeah, which it stand. Visibly. Amen." (7.60)
A statue of a Confederate soldier stood to the right of the walk that led up to the courthouse door. Above the head of the statue, national, state, and Confederate flags flew on long metal poles. (9.11)
As we walked up to the entrance of the school, I saw two boys taking in the flag. (12.33)
I walked between the parked cars and passed the statue of the Confederate soldier and the state, national, and Confederate flags. (22.108)
They stood by the minister's car, near the statue of the Confederate soldier and the three flags. The flags hung limp beneath the overcast sky. (24.1)
It's almost like he's trying to drive home the point that the bitter injustice and extreme poverty are happening right here in the United States, and that the government flies its flag and authority over people that have very few rights.
For example, he says that, in school, "The flag hung limp from a ten-foot bamboo pole in the corner of the white picket fence that surrounded the church" (5.1). The flag isn't flying proudly; it's hanging limp. Usually a flag is flown with pride, to show a nation's strength and power. Here, though, the flag is just dangling, no wind to make it wave and show its colors. It's almost like the nation is tired or weak, like the sad, limp flag.
Later, heading into the courthouse, he takes note of "the statue of the Confederate soldier and the state, national, and Confederate flags" (22.108). This underlines the fact that Grant still lives on a plantation even though slavery had been abolished about eighty years before, and is treated like a second-class citizen because of his race.
Even though the Confederacy, and slavery, were dissolved at the end of the Civil War, this Louisiana town is still stuck in the past, flying the flag of a confederacy that no longer exists and that would not recognize any of Grant's rights as a citizen because he is black. That Confederate flag waving over the courthouse says that the rights being defended inside of it don't necessarily belong to the black citizens of Louisiana.
This symbol helps explain why no one tries to fight Jefferson's sentence, but rather just accepts it as another injustice from the government. The symbolic power of the Confederate flag flying over the courthouse shows the heavy weight of history on the town of Bayonne.