By Robert Iafolla

(Reuters) - A federal appeals court upheld a Kentucky county’s so-called right-to-work ordinance on Friday, clearing the way for local-level laws that restrict labor unions' role in the workplace.

The 6th U.S. Circuit Court of Appeals in Cincinnati, Ohio ruled that federal labor law does not block Hardin County from banning the use of agreements between employers and unions that require workers to join a union.

A 6th Circuit panel composed of three Republican-appointed judges ruled that counties enjoy the same rights as states to enforce right-to-work laws that forbid these so-called union security agreements.

The panel reversed a decision by U.S. District Judge David Hale in Louisville, Kentucky, an Obama appointee, who struck down the ordinance in February after a challenge by a coalition of unions led by a United Auto Workers affiliate.

Friday's ruling was a blow to unions, which could face broad changes to labor regulations with Republican Donald Trump as President and Republicans in control of Congress.

Trump has expressed support for right-to-work legislation. Republican leaders in Congress have consistently sought a national right-to-work law, although Democrats are expected to try to block such attempts, labor law experts said.

Twenty-five states have right-to-work laws. Labor unions say the laws are designed to undermine collective bargaining and workers’ rights.

Lawmakers in Kentucky have tried and failed to pass a statewide law. The state became a testing ground for local laws after Warren County passed the nation's only county ordinance in December 2014. Hardin County and 10 others in the state soon followed suit with nearly identical measures.

The Kentucky counties adapted their ordinances from a model bill developed by the American City County Exchange, an offshoot of the American Legislative Exchange Council, an influential conservative policy group.

The ruling allows local right-to-work laws in the two states in the 6th Circuit without them at the state level – Kentucky and Ohio – and could fuel efforts to pass similar measures elsewhere.

“While most of us thought the fight over right-to-work would occur in the halls of Congress, new fronts in the fight could be opened up in county commissions and county legislatures all across the United States,” said Seth Harris, a former Acting U.S. Labor Secretary during the Obama administration.

The unions will likely ask the entire 6th Circuit to reconsider the case, said Irwin Cutler, a lawyer for the unions in the case. Lawyers for Hardin County could not immediately be reached for comment.

The case is UAW v. Hardin County, 6th U.S. Circuit Court of Appeals, No. 16-5246.

(Reporting by Robert Iafolla in Washington, Additional reporting by Daniel Wiessner in Albany, New York, Editing by Alexia Garamfalvi and Andrew Hay)