States now must report undocumented immigrants to DHS or risk federal funding, DOJ says

All states going forward must report undocumented immigrants known to be in a state to the U.S. Department of Homeland Security or risk losing federal funding for programs meant to aid low-income individuals, the Department of Justice said in a new legal opinion.

The DOJ, in issuing the opinion, revised the Office of Legal Counsel's prior opinion from 1998, which found that only specific state agencies that administered the Temporary Assistance for Needy Families and the Supplemental Security Income programs needed to provide information to federal immigration authorities.

"Congress wrote this requirement plainly," Assistant Attorney General T. Elliot Gaiser of the DOJ's Office of Legal Counsel, said in a statement.

"When a state chooses to participate in TANF, it accepts the obligation to report illegal aliens in the United States," Gaiser said. "Tax dollars intended to help vulnerable Americans should not perversely encourage illegal entry into the United States, but rather should reinforce our laws and our borders."

The DOJ in a statement Wednesday said the Office of Legal Counsel's Sept. 1 opinion "explains that Congress defined 'State' broadly in the Personal Responsibility and Work Opportunity Reconciliation Act of 1996."

"As a result, when a state accepts federal TANF or SSI funds, the entire state government — including all component agencies — is bound by federal law to share information with DHS about individuals the state knows to be not lawfully present," the DOJ said.

The new opinion only applies proactively, not to past enrollments in TANF and SSI.

All 50 states, the District of Columbia and several U.S. territories participate in both programs. Federal TANF funding grants top $16.4 billion annually, according to the DOJ.

"Our clarification does not impose new obligations on states," said Deputy Assistant Attorney General Joshua Craddock, the Office of Legal Counsel official who wrote the new opinion.

"It simply restores the original meaning of the statute Congress enacted and ensures that DHS receives the information it is legally entitled to," Craddock said.

"States that accept TANF funding must abide by federal law, and failure to comply may lead to serious consequences, including loss of program funding."

CNBC has requested comment on the new opinion from the attorneys general of more than a dozen of the largest U.S. states, and asked if they will challenge its guidance.

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