This detail tells us several crucial things about government in this story.
First, it tells us the government in this story is still technically the government of the United States. This is not some alien world or another country with a different legal tradition.
This also suggests the oppressive actions the government in this story take come from principles and ideals that already exist in the United States.
Third, the number 213 is extremely high. Right now, there have only been 27 amendments to the Constitution, and when Vonnegut wrote the story, there were even fewer (22). This means there has been a tremendous amount of change in the intervening years. The government in this society has introduced change after change, modification after modification. It suggests democracy is out of hand, and the people are making changes to get what they want that ignore the core principles upon which America was founded.
Finally, this means this is a government that keeps the appearance of legitimacy, but which is now hollow. This fits the story; the kind of equality the handicappers enforce is not the kind written into the original Declaration of Independence or Constitution.