Bernice Todd’s Choctaw family roots are sunk deep in the soil of Oklahoma, a state whose very name is Choctaw for “red people.” But in the middle of a debilitating battle with cancer, Todd, a 39-year-old who cleans homes at a trailer park and baby-sits for a living, lost her state Medicaid health care coverage because, although she’s a Native American, she could not prove she is a U.S. citizen.

As I was asked today, my paternal grandmother was Choctaw Black Seminole, my maternal grandmother Apache. I am a mutt, the White Man’s legacy.

While Todd’s case is rich in irony, she is one of tens of thousands of Americans who are falling victim to a new federal rule—aimed at keeping illegal immigrants off the Medicaid rolls—requiring that recipients prove their citizenship and identity with documents many don’t have.

States have always been required to check a Medicaid applicant’s eligibility, which includes citizenship. But a July 2006 rule, enforced by the federal Centers for Medicare & Medicaid Services (CMS), now demands specific documents as proof, such as a passport or a birth certificate, driver’s license or military record. States face fines if they don’t comply.