Strange as it may seem, in the U.S. Constitution there is no requirement for states to let voters participate in a presidential election. At least 7 of the original 13 states chose their electors through some method other than a popular election, such as having the electors selected by the legislature or appointed by the governor.
The Constitution isn't kidding when it says: "Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors (etc.) ..."
You’re omitting state law and the requirements thereof now, as well as ignoring the Tenth Amendment. Also, there’s a difference between being a “faithless elector” and a fraudulent one.
Did you look up what happened in “Bleeding Kansas” yet?