What natural law? Voting is a right in a republic or a democratic government that uses the word, people as in "We the people...". I repeat a citizen has a right to vote. Read the constitution ...
Section 2. The House of Representatives shall be composed of members chosen every second year by the people of the several states,
That process is known as voting.
And the fifteenth amendment
The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude--
Voting is a right of citizens.
And the fifteenth amendment
The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude—
My point precisely.
Number one, it is the fifteenth amendment. Two, there are numerous reasons for states to deny the vote to any number of people outside the mandated race, color, or previous condition of servitude. Crooks, morons, children, unregistered, wrong district, no picture ID, and women to name another controversial addition to the amendment list above and beyond the first ten.
The list goes on, and states do indeed reduce the number of voters. All is fine as long as they don’t refuse based on the mandated race, color, or previous condition of servitude. The narrower the list of authorized voters the easier it is to track dishonest or manipulative schemes to skew the results, and the better I like it.