Chicago ? No one has been able to figure out when Kevin Harris was born or where. This blind, mentally impaired man has told the Cook County Public Guardian he doesn’t know. Public records searches have come up empty.

Until now, this hasn’t been a problem for Harris, who depends on Medicaid – the nation’s largest health care program – for medical care and his community-based living arrangement.

But come Saturday, Harris’ setup could be jeopardized. That’s the startup date for a controversial new law that requires as many as 50 million Medicaid recipients to prove they are U.S. citizens by providing passports, birth certificates, driver’s licenses or other documents to authorities. All new applicants also have to provide proof of citizenship before their request to join Medicaid is considered.

As a result of the new law – an effort to keep illegal immigrants from finding their way onto the Medicaid rolls – consumer advocates warn that many vulnerable Americans could lose or be denied Medicaid coverage.

Especially at risk, they say, are seniors in nursing homes, the severely disabled, children in foster care, the homeless, blacks and American Indians born outside of hospitals and Hurricane Katrina refugees who have lost everything, including important personal records.

Harris, believed to be about 42, doesn’t have any of the papers the government says it needs to establish citizenship. Efforts to find a birth certificate in Illinois, where he was adopted, have failed. His state identification card was stolen years ago. He doesn’t have a passport. And the public guardian’s office says it knows of no relatives or close associates who could tell the circumstances of his birth.

“The horrible thing is these people have lived in this country all their lives and no one would question that they’re Americans, but they don’t have the ability to provide the documentation,” said Cook County Public Guardian Robert Harris.

The controversy about the new Medicaid law is an offshoot of the heated national debate on illegal immigration, and it illustrates how social policy is being influenced by that discussion.

The intent of the statute, signed by President Bush in February, is to prevent illegal immigrants from obtaining medical care through Medicaid by falsely claiming to be U.S. citizens, explained John Stone, spokesman for Rep. Charles Norwood, R-Ga., a leading sponsor. Only U.S. citizens and some legal immigrants are eligible to receive Medicaid benefits.

“Medicaid programs across the country face a funding crisis, and the feedback we’re getting is that a lot of the financial pressure is coming from illegal immigrants,” Stone said.

Not so, consumer groups counter, citing a June 2005 report from the U.S. Department of Health and Human Services inspector general that found no evidence of widespread citizenship fraud in Medicaid.

But the potential for fraud exists, the report acknowledged, because 40 states allow Medicaid applicants to assert they are citizens without providing any kind of proof. Another six states often allow similar assertions. Only Georgia, Montana, New Hampshire and New York currently have documentation requirements.

“The problem is, the enforcement of existing regulations has been almost nonexistent,” said Rep. Nathan Deal, R-Ga., another key sponsor.

What happens next is uncertain. Government guidelines issued earlier this month indicate that current Medicaid members will get some time to obtain documents, but it’s not clear yet how long that will be.

Consumer advocates had hoped the guidelines would be flexible, but they’re “incredibly prescriptive and burdensome,” said Stephanie Altman, policy director with Chicago’s Health & Disability Advocates. Her group and four others plan to file a legal challenge to the new law Wednesday in federal district court in Chicago.