The Boston Globe offers this report on U.S. Attorney Bradley Schlozman and voter fraud indictments brought in Missouri just before the 2006 election. I’ve linked to earlier articles on this aspect of the U.S. attorneys/voter fraud controversy before, but something new in this article is buried near the end of the article:

Critics later accused Schlozman of violating the Justice Department’s own rules. A 1995 Justice election crime manual says “federal prosecutors . . . should be extremely careful not to conduct overt investigations during the preelection period” to avoid “chilling legitimate voting and campaign activities” and causing “the investigation itself to become a campaign issue.”
“In investigating election fraud matters, the Justice Department must refrain from any conduct which has the possibility of affecting the election itself,” the manual states, adding in underlining that “most, if not all, investigation of alleged election crime must await the end of the election to which the allegation relates.”
The department said Schlozman’s office got permission from headquarters for the election-eve indictments. It added that the department interprets the policy as having an unwritten exception for voter registration fraud, because investigators need not interview voters for such cases.

My emphasis. I have never heard of this before. Even if it were a good policy for the department to have such an exception (a principle I’m quite dubious about if the main purpose is to avoid “chilling legitimate voting and campaign activities” or causing “the investigation itself to become a campaign issue”), there’s no reason to have an unwritten policy in this regard. Indeed, having an unwritten policy opens up DOJ to charges that the unwritten policy is politically motivated and inconsistently applied.