Final answer:
The Supreme Court case National Federation of Independent Business v. Sebelius served as a justification for the policy initiative of mandating health insurance. The Court ruled that the individual mandate to purchase health insurance was permissible under Congress's power to tax.
Step-by-step explanation:
The justification for the policy initiative of mandating health insurance can be found in the Supreme Court case National Federation of Independent Business v. Sebelius. In this case, the Supreme Court upheld the Affordable Care Act (ACA) as a constitutional extension of Congress's power to tax. The individual mandate to purchase health insurance was found to be permissible under Congress's authority to tax.