What made it legal to remove the right to vote?

Question

What law, statute, legislation or whatever made it legal / constitutional to remove the right to vote from a person convicted of a felony?

Answer 1

A felon cannot vote because there will be costly security contingent to secure a felon to vote in every election which is not a practical step in favor of government. Likewise, disqualification to exercise the right to vote is a penalty that goes with imprisonment under the Rules of Court.