The fact is that no president should ever promise not to involve himself in DOJ decisions, since under the Constitution the president is the chief law enforcement officer in the country, and the DOJ works for him. He is literally supposed to be ultimately in charge of the DOJ. The Democrats, however, would like to circumvent the Constitution on this issue (as on so many others) and, in effect, make the DOJ a fourth branch of government. People may not like this constitutional arrangement, but the way to change it is by means of a constitutional amendment, not by simply ignoring the Constitution.