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Mexican prosecutors on Thursday declared completely unfounded the U.S. case against a former defense secretary arrested on drug charges in the United States and then returned under pressure from the Mexican government.

Few had ever expected Mexico to really prosecute influential former Defense Secretary Salvador Cienfuegos. President Andrés Manuel López Obrador has relied more on the army than any other recent president, trusting it with everything from infrastructure projects to operating airports and trains.

Some thought Mexican prosecutors might dismiss the case on technical grounds of inadmissible evidence. But they went further than that, absolutely clearing Cienfuegos of accusations that he helped a drug cartel in return for bribes in a move that could mar Mexico’s already-bumpy relations with the United States in the post-Trump era.

In a surprisingly quick process, Mexico’s Attorney General’s Office announced that Cienfuegos presented evidence in five days that it said completely disproved what it described as a seven-year U.S. investigation of the now-retired general.

“The conclusion was reached that General Salvador Cienfuegos Zepeda never had any meeting with the criminal organization investigated by American authorities, and that he also never had any communication with them, nor did he carry out acts to protect or help those individuals,” the office said in a statement.

It said Cienfuegos had not been found to have any illicit or abnormal income, nor was any evidence found “that he had issued any order to favor the criminal group in question.”

All charges were dropped and Cienfuegos, who was never placed under arrest after he was returned by U.S. officials, is no longer under investigation.

Cienfuegos was arrested in Los Angeles in October, after he was secretly indicted by a federal grand jury in New York in 2019. He was accused of conspiring with the H-2 cartel in Mexico to smuggle thousands of kilos of cocaine, heroin, methamphetamine and marijuana while he was defense secretary from 2012 to 2018.

Prosecutors said intercepted messages showed that Cienfuegos accepted bribes in exchange for ensuring the military did not take action against the cartel and that operations were initiated against its rivals. He was also accused of introducing cartel leaders to other corrupt Mexican officials.

Under the pressure of Mexico’s implicit threats to restrict or expel U.S. agents, U.S. prosecutors dropped their case so Cienfuegos could be returned to Mexico and investigated under Mexican law.

Acting U.S. Attorney Seth DuCharme told a judge at the time, “The United States determined that the broader interest in maintaining that relationship in a cooperative way outweighed the department’s interest and the public’s interest in pursuing this particular case.”

Even though the U.S. yielded on Cienfuegos, Mexico’s Congress a few weeks later passed a law that will restrict U.S. agents in Mexico and remove their diplomatic immunity.

Mike Vigil, the Drug Enforcement Administration’s former chief of international operations, said clearing Cienfuegos “could be the straw that broke the camel’s back as far as U.S.-Mexico cooperation in counter-drug activities.”

“It was preordained that Mexican justice would not move forward with prosecuting General Cienfuegos,” Vigil said. “It will greatly stain the integrity of its judicial system and despite the political rhetoric of wanting to eliminate corruption, such is obviously not the case. The rule of law has been significantly violated.”

López Obrador had a close, friendly relationship with U.S. President Donald Trump, and waited longer than almost any other world leader to congratulate Joe Biden on his election. The restrictions on U.S. agents, and López Obrador’s veiled warnings to the Biden team to stay out of Mexican affairs, appeared to foreshadow thorny relations. The Cienfuegos decision may only add to that perception.

Cienfuegos, a general who led Mexico’s army department for six years under President Enrique Peña Nieto, was the highest-ranking former Mexican Cabinet official arrested since top security official Genaro Garcia Luna was arrested in Texas in 2019.