The Mexican Football Federation is standing by its decision.
The federation plans to defend its decision to clear five players who tested positive for the anabolic agent clenbuterol in training camp for the Gold Cup.
The World Anti-Doping Agency said last week it would challenge the Mexico federation's decision not to ban the five players for doping. The federation argues that contaminated meat caused the positive tests.
"In our matter, it's a clear case of contamination," Mexico secretary general Decio De Maria said. "The facts in our country support this."
WADA has appealed the case to the Court of Arbitration for Sport in Switzerland. No date has been set for a hearing.
De Maria, citing Mexican health officials, said 66.7 percent of blood and urine samples taken from cattle showed positive results.
"Clenbuterol contamination in beef is getting more frequent," De Maria said. "This is what happened and why there were no sanctions. It is going to be a long, expensive case, but we are certain our decision was correct faced with contamination like this. This is an accident and it should not be punished under the doping code."
The five internationals tested positive for the banned anabolic agent at a May training camp before the Gold Cup.
Goalkeeper Guillermo Ochoa, defenders Edgar Duenas and Francisco Rodriguez, and midfielders Antonio Naelson and Christian Bermudez were suspended in June during the Gold Cup and were dropped the squad, then had their suspensions lifted a month later.
The Mexico case is WADA's second high-profile challenge to a legal defense of eating tainted meat.
WADA and the International Cycling Union appealed to CAS after 2010 Tour de France winner Alberto Contador blamed contaminated steak for his clenbuterol positive, and was exonerated by the Spanish cycling federation. That case is scheduled to be heard in November.
The World Anti-Doping Code typically requires suspensions of up to two years for first-time offenses, or four years in cases of systematic doping programs.
Mexico President Felipe Calderon has acknowledged that contamination with clenbuterol is a problem in the country, where it is used to bulk up livestock.
Based on reporting by The Associated Press.