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 ban convicted criminals, especially felons, from voting for a fixed period of time or indefinitely.[3] The number of American adults who are currently or permanently ineligible to vote due to felony convictions is estimated to be 5.3 million.[4] Some states also have legacy constitutional statements barring legally declared incompetent from voting; such references are generally considered obsolete and are being considered for review or removal where they appear.[5]