Caldwell was one of 13 state attorneys general who initiated a 2010 lawsuit challenging the constitutionality of the Patient Protection and Affordable Care Act. The suit argued that the individual mandate fell outside of the federal government’s authority and that the requirement for state Medicaid expansion of coverage violated state sovereignty. The case was ultimately heard before the Supreme Court, which ruled to uphold the individual mandate as falling within Congress’ authority to levy taxes and struck down the Medicaid expansion as being unduly coercive in light of the withholding of funding that would result from noncompliance.