I'm honestly perplexed by your answer here - did you read the Fortune article? It has quoted sources and emails to back up the fact that state prosecutors refused to allow the ATF agents to do anything with these gun runners. That is, they told them that buying a large amount of guns was legal, and that even transferring them to someone else was legal as well.

If the state DA isn't will to prosecute, then what would you suggest the ATF agents do? And if the ATF agents know that guns are being purchased, but then cannot arrest those individuals because they do not have probable cause, why would you call that "allowing the guns to walk"?