Sen. Bob Menendez (N.J.), the top Democrat on the Senate Foreign Relations Committee, lambasted the Trump administration Wednesday over its decision to release a former Mexican defense secretary accused of drug trafficking.

The Department of Justice announced Tuesday that it would drop charges against Gen. Salvador Cienfuegos and allow him to return to Mexico "so that he may be investigated and, if appropriate, charged, under Mexican law."

"After four years of President Trump’s empty boasting that he stands for the rule of law, his term ends with his administration once again turning a blind eye to the facts and selling out U.S. national security interests," Menendez said in a statement.

"For someone who launched his entire presidency by conjuring xenophobic images of druglords running amok along the U.S.-Mexico border, there is no explanation for Attorney General [William] Barr’s decision to abruptly drop drug trafficking charges against General Cienfuegos," he added.

Cienfuegos led Mexico's Secretariat of National Defense, which oversees the Army and Air Force, from 2012 to 2018 under former President Enrique Peña Nieto.

His arrest in Los Angeles last month delivered a blow to current President Andrés Manuel López Obrador, who has relied on the military for many of his government projects, from building an airport to manning his public security apparatus, the National Guard.

The arrest also threatened to block the expansion of military-to-military relations between the United States and Mexico, a component of security cooperation that Mexican forces have approached with extreme suspicion.

U.S. District Judge Carol Amon of the Eastern District of New York on Wednesday granted the Department of Justice's motion to withdraw the case, which prosecutors had previously characterized as "strong."

Menendez said the about-face to release Cienfuegos, who was charged with taking bribes and aiding a cartel to traffic cocaine to the United States, would further hurt an already shaky relationship.

"Cooperation with the Mexican government is essential for upholding our national security, and those bilateral ties must be built on common respect for our own rule of law and due process," he said. "Attorney General Barr risks undermining that faith in the U.S. justice system and encouraging impunity at the highest levels in Mexico."