In a sharply worded federal complaint, the Union Pacific Railroad Co. asserts that it is not responsible for the cocaine and marijuana seized on railroad cars as part of a smuggling operation of trains bound for the United States from Mexico.

U.S. Customs and Border Protection found 47 cases of illegal narcotics seized at checkpoints in California, Arizona and Texas. In each case, the Border Patrol found illegal drugs on a train bound for the United States from a Mexican railroad.

Though the trains were ultimately headed to Union Pacific customers, the railroad company claims that it should not have to pay the $37.7 million in proposed penalties against it, because the drugs were found before the railroad cars ever came into Union Pacific's possession.

"At all times prior to the discovery of the illegal narcotics, either the Mexican railroad operating the train of (U.S. Customs and Border Protection) had exclusive control of the trains in which they were found," the plaintiff claims.

It rejects the defendant's assertion that Union Pacific failed to exercise the "highest degree of care and diligence" to ensure drugs were not smuggled on its trains. Union Pacific points out that it owns no railroad facilities in Mexico, and cannot hire, supervise or direct the railroad employees across the border.

The government improperly applied the Tariff Act of 1930 in assessing fines against Union Pacific, the lawsuit claims.

"The Tariff Act does not obligate (Union Pacific) to enter Mexico and conduct extraterrestrial inspections," the railroad claims, "and to do so would require (Union Pacific) to take extraordinarily dangerous and costly measures that the United States itself has found too dangerous and/or futile to undertake."

The risk of setting up security operations in Mexico would expose the plaintiff and its employees "to the risks of murder and mayhem at the hands of Mexican drug cartels, while at the same time potentially running afoul of Mexican law," the lawsuit states.

And it would accomplish nothing, the railroad claims.

"If (U.S. Customs and Border Protection) and the full power of the United States government cannot effectively seize drugs in Mexico, there is no reason to believe that (Union Pacific) could.