They essentially tell them that the person is an asset to the United States Government and should be left alone because the work they are doing for the USG is m

They essentially tell them that the person is an asset to the United States Government and should be left alone because the work they are doing for the USG is more important than anything else they may be involved in. There are some good quotes in The Politics of Heroin. Things like (paraphrasing), "We are not generally in the habit of attempting to build criminal cases against our strategic allies."