NASHVILLE, Tenn. -- The state may not have done its homework when it comes to a new law on hiring illegal immigrants.

Video: State Discovers Immigration Law Not Enforceable

Workers from Ray Bell and Associates are widening a bridge in Maury County. It's a $2.5 million project paid for with taxpayers’ dollars.

Under a new law that took effect in October, all state contractors like Ray Bell Construction have to pledge in writing that they don't hire illegal immigrants and that neither do their subcontractors.

"We want contractors to know, if they are going to do business with the state of Tennessee that they cannot hire illegal immigrants.” said Mike Morrow of Tennessee’s Office of Finance and Administration.

But the state recently discovered that it's a law that cannot be enforced.

Gov. Phil Bredesen signed an executive order giving the state the power to do random checks of companies' personnel records, but seven months later, the random checks haven't started yet.

According to the state, they didn't realize it has no right to look at the employment forms it needs to see.

When applying for a job, potential employees check a box on an I-9 form saying whether or not he or she is a citizen of the United States.

"We started down the path of using the I-9s that an employer is required to get per federal law and found out that information is not available to us. It's only for federal purposes,” Morrow said.

The state said it is a setback and that they're trying to find other ways to determine which employees are legal and which aren't.

"It's going to be difficult,” Morrow said.

The state said the Department of Labor could verify Social Security numbers in the employers’ files, but that program is still not up and running. A state representative said that process could begin later this month.

Ray Bell's head of human resources told Channel 4 News that they double-check workers' Social Security numbers.

They said that employers are also concerned with identity theft being so common.