Which branch determines voter eligibility and election rules?

The eligibility of an individual for voting is set out in the constitution and also regulated at state level. The constitution states that suffrage cannot be denied on grounds of race or color, sex or age for citizens eighteen years or older. Beyond these basic qualifications, it is the responsibility of state legislatures to regulate voter eligibility. Some states bar convicted criminals, especially felons, from voting for a fixed period of time or indefinitely. The number of American adults who are currently or permanently ineligible to vote due to felony convictions is estimated to be 5.3 million.[1] Some states also have legacy constitutional statements barring the "insane" or "idiots" from voting; such references are generally considered obsolete and are being considered for review or removal where they appear.