Which is why it has to be done as a regulation/tax. Make it super attractive to go with the plan, and super repulsive to try to shoulder the issue independently. But it can’t absolutely ban you going independent.
It is a penalty administered by the IRS. Which is a new role for the IRS. Then Chief Justice Roberts legislated from the bench and decided it was a tax, a tax for which all are liable (a head tax - without an authorizing Amendment) the payment of which is waived upon their contracting with a business for a service (health insurance).
Compulsion to contract is illegal. Direct taxes require an Amendment.