The U.S. Chamber of Commerce, the Oklahoma Restaurant Association, and the Oklahoma Hotel and Lodging Association, among others, say immigration enforcement should be left to the federal government, not the states, Legal Newsline reported Wednesday.

The groups say the Oklahoma law, which requires employers to verify the immigration status of employees and contractors or subcontractors, forces them to use the voluntary federal online verification system to determine workers' legal status.

The law, which isn't being enforced, also requires that businesses with state contracts to withhold income taxes of contractors and subcontractors if they don't use the federal verification system.

"Federal regulation of the employment of aliens leaves no room for state interference," Robin Conrad, executive vice president of the National Chamber Litigation Center, told Legal Newsline. "Federal law broadly pre-empts the field of employment verification and any attempt by states to meddle in this domain is unconstitutional."

She said states shouldn't take an independent approach to immigration policy.

"A patchwork of conflicting and inconsistent state laws is not the answer," Conrad was quoted by Legal Newsline as saying.