Controlling shareholders at Mexican airport operator Grupo Aeroportuario del Pacifico (GAP) are fighting a takeover bid by copper mining company Grupo Mexico that is mired in a complicated court battle.

Grupo Mexico has steadily been buying shares of GAP -- so far acquiring a 23 percent stake -- even though GAP's bylaws say no noncontrolling shareholder should own more than 10 percent of the company.

In June, Grupo Mexico told the Mexican stock exchange it planned to buy more than 30 percent of the airport operator, triggering a rule obligating Grupo Mexico to make an offer for the entire company.

Grupo Mexico is buying up B series shares that are available on the open market but it cannot acquire BB shares, held only by controlling partners.

The BB shareholders are Mexican and Spanish groups that are fighting each other for administrative control of GAP.

But they are both united against Grupo Mexico's bid.

"We have no intention to sell our participation," Vicente Corta, the lawyer for the Mexican shareholders, told Reuters. "And as far as I understand, the Spanish shareholders have no intention to sell either."

"There are many reasons that offer shouldn't move forward," Corta said. "Most importantly, because it violates GAP's own statutes."

GAP said afternoon that two of its board members had resigned but did not say why.

Grupo Mexico is challenging GAP's bylaws in court. GAP has lashed back by filing an appeal to try to stop the offer.

Regulators would still have to approve the deal, which is mired in legal battles.

Grupo Mexico said in its second-quarter earnings report that the Mexican National Banking and Securities Commission, known as the CNBV, ruled that GAP's bylaws limiting share ownership to 10 percent should be modified.

A spokesman for the CNBV could not confirm that.

Sweeter Deal?
Grupo Mexico -- which operates Mexico's largest railroad, as well as copper mines in Mexico, Peru and the United States -- said it would pay a maximum of 50 pesos each for the GAP shares, which were trading at 47.65 pesos on Wednesday afternoon.

Chief Financial Officer Daniel Muniz told investors on Wednesday there are no plans to raise the bid price.

But some analysts think Grupo Mexico may sweeten the deal.

"Considering the mining company's interest in the airport sector ... we don't rule out the possibility that they could increase their offer in the coming months," BBVA Bancomer said in a research note.

In its original announcement, Grupo Mexico said it would drop the offer if it could not acquire more than 50 percent of GAP's shares, although it insists it does not want operational control of the company.

"Our idea at this point is not to take control, not to operate the company. We are happy with the way the company is operated; we think they are doing a good job. We like the asset. We like the industry," Muniz said on a quarterly call.

"We are launching a 100 percent tender offer because that is a legal requirement under Mexican law," he said.

The company's transportation business was recently strengthened by a ruling allowing for the merger of its two railroad units.

Grupo Mexico has floated the idea of launching an initial public offering for the division, but Muniz said there are no concrete plans yet. (Reuters)