Issa asked Holder to see the letter assigning him/her to the investigation which would necessarily include its scope. Holder said there was no such document, that it was tasked verbally. Meaning: “Investigate, but not too much and protect me.”
Also, I think Holder expects to use this to deflect the sh!t that will fall on his head at this month's Congressional hearing. It won't work and there will be more charges of whitey racism.