LOUISVILLE, Ky. (WDRB) -- Trade groups representing Kentucky stores and restaurants are asking a judge to stop Louisville's minimum wage ordinance from taking effect July 1.

The challenge was filed Feb. 13 by the Kentucky Retail Federation, Kentucky Restaurant Association and Park Hill-area business Packaging Unlimited.

The ordinance – which will gradually raise the minimum wage in Jefferson County to $9 per hour in 2017 – conflicts with Kentucky's Wage and Hours Law and is “null and void," according to the suit filed in Jefferson Circuit Court.

The suit asks for an injunction to keep the ordinance from taking effect and for it to be thrown out permanently.

Employers throughout the county are to begin paying at least $7.75 an hour on July 1, followed by $8.25 on July 1, 2016, and finally $9 on July 1, 2017, according to the ordinance. The current minimum wage in Kentucky is the same as the federal -- $7.25.

Mayor Greg Fischer signed the ordinance Jan. 2 after telling the Metro Council he would veto the initial proposal of $10.10 per hour favored by some Council Democrats.

Tony Hyatt, spokesman for the Council's Democratic caucus, said the legal challenge comes as no surprise. He noted that, as the ordinance was debated, Jefferson County Attorney Mike O'Connell's office advised the council that metro government had the power to set a local minimum wage.

“The County Attorney gave the green light, and that's why the sponsors moved forward,” Hyatt said.

Fischer spokesman Chris Poynter said the mayor's staff hasn't seen the lawsuit yet.

The retail and restaurant associations referred comment to their lawyer, Brent Baughman.

"There is a principle to be defended here, which is that the Metro government doesn't have the authority to go its own way" on the minimum wage, Baughman said.

Baughman said it's possible Jefferson Circuit Court Judge Judith McDonald-Burkman could rule on the merits of the case before July 1. He said it's just a matter of legal interpretation, and no facts are needed to flesh out the case.

Packaging Unlimited CEO Pete Hanekamp did not immediately return a call.

Copyright 2015 WDRB News. All rights reserved.