The more I learn on this, the more it is going to be a can or worms, or worse.
Under the constitution, each state dictates its own election laws. Example, the SOS of Maine has the power and duty under Maine law to ban someone ineligible from a ballot. The Michigan SOS does not, and could not, even prevent a 12-year-old from being on a presidential primary ballot.
SCOTUS will be hearing and ruling on the Colorado case only. Because every state has their own election laws (states rights, and how the constitution is written), it's going to be a mess, in the same manner that abortion rights varies from state to state.
If you got 30 minutes, listen to this explanation, from a former federal prosecutor.