According to this report, one apparently does not really have to prove citizenship in order to vote in Kansas:
The law in question allegedly violates the National Voter Registration Act and the 14th Amendment.
Well, here is the part of the 14th Amendment I think applies. Note that it specifically mentions voters who are CITIZENS:
2. ... when the right to vote at any election for the choice of electors for President and Vice President of the United States, Representatives in Congress, the Executive and Judicial officers of a State, or the members of the Legislature thereof, is denied to any of the male inhabitants of such State, being twenty-one years of age, and citizens of the United States, or in any way abridged ...
And here is a link to the National Voter Registration Act of 1993:
It appears to say that one cannot register to vote unless they are a citizen.
So, exactly what is the problem in Kansas? Beats the hell out of me.