In 2012, in its first ruling on the Affordable Care Act, the court hamstrung Congress’s expansion of Medicaid eligibility from the very poor to the working poor by effectively making expanded coverage optional for states. About 2.2 million people are uninsured as a result, nearly 90 percent of them in Southern states whose economies have always relied on low-cost labor. About half of those left out of the Medicaid expansion are black or Hispanic.

These cases are part of a longer historical arc: the dismantling of the legal legacy of the New Deal and the creation of law for a new Gilded Age. A hundred years ago, the last time economic inequality was as stark as it is today, the Supreme Court struck down minimum-wage laws and other workplace protections. Justices insisted those laws violated workers’ free agreements to work for less money and less security — like the agreements in Epic Systems to take wage-theft complaints to a private arbitrator. The court struck down a national ban on child labor, claiming the Constitution left states free to set their own policies — as in the Medicaid expansion a century later. The defense of child labor came out of the South, which was then building its economic advantage on cheap and vulnerable labor.

The New Deal shook American law. Its triumph brought new attention to economic power. Antitrust law worked to cut back corporate concentration and control. Labor unions were essential to what the Progressive-Era jurist Louis Brandeis called “industrial democracy” — democracy adapted to a complex modern economy.

Congress could set national standards for the workplace and the social safety net. These were closely linked, because everyone understood that workers who lose health care, housing or even food if they lose their jobs are much more vulnerable than those with basic entitlements. Citizenship itself was threatened if companies could dominate their workers. Justice Felix Frankfurter captured this vision in 1961, when he wrote of a union dispute, “The notion that economic and political concerns are separable is pre-Victorian.”

Some people still imagine “workers” as white men, but the American working classes are increasingly female, immigrant and nonwhite. There’s no separating these hierarchies.

The 1970s brought a swing back toward inequality. The court stopped the advance of the civil-rights revolution at the borders of poverty. It ruled that there was no constitutional right to welfare or other social support and that public-school funding schemes that kept schools poor in poor neighborhoods and rich in rich ones did not discriminate unconstitutionally against poor people. Amid a constitutional revolution of legal equality, the court gave its blessing to the oldest form of inequality, between haves and have-nots.