You do not have to buy the “federal” policy, you do have to maintain a policy that is compliant which can be obtained outside the federal exchanges through state or private companies.
Without the Law OP listed this would be a single payer system.
This is the law you are missing to fill the info gap.
Little Snip; (a) Requirement to maintain minimum essential coverage
An applicable individual shall for each month beginning after 2013 ensure that the individual, and any dependent of the individual who is an applicable individual, is covered under minimum essential coverage for such month.
(b) Shared responsibility payment
(1) In general
If a taxpayer who is an applicable individual, or an applicable individual for whom the taxpayer is liable under paragraph (3), fails to meet the requirement of subsection (a) for 1 or more months, then, except as provided in subsection (e), there is hereby imposed on the taxpayer a penalty with respect to such failures in the amount determined under subsection (c).
Bla bla bla...
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link to www.law.cornell.edu]