The first paragraph of the latest AP article sums it up:
A newly disclosed effort to keep Vice President Dick Cheney's visitor records secret is the latest White House push to make sure the public does not learn who has been meeting with top officials in the Bush administration.
The Bush administration has changed the rules over record-keeping to prevent access to visitor records. They've usurped the role of the Secret Service, which is covered by the Freedom of Information Act (FOIA). Instead, Bush and Cheney claim visitor records are under their jurisdiction, thus exempt from FOIA. CREW is not accepting that determination, hence our lawsuits.