Is Ukraine selling half of its U.S.-supplied weapons to Mexican cartels?

There is no evidence that half of the weapons supplied to Ukraine by the United States are being sold to Mexican cartels or other criminal organizations. The Department of Defense, including nearly 100 individuals from its Office of Inspector General, closely monitors weapons and military assistance supplied to Ukraine alongside several other agencies. 

Black market weapons sales tend to increase in conflict zones, and some organized arms trafficking by criminal organizations has been reported in Ukraine. These operations primarily involve small, Soviet- or Russian-style weapons recovered on battlefields or weapons dumps, however, rather than the missiles and ammunition that make up most of the U.S.-supplied arsenal. 

Similar claims, including that weapons supplied to Ukraine by NATO countries were being sold to criminal organizations, circulated at the start of the war and were later traced back to Russian disinformation campaigns.