The Obama administration is fighting to block access to names of visitors to the White House.

The Secret Service has denied msnbc.com's request for the names of all White House visitors from Jan. 20 to now. It also denied a narrower request by the nonpartisan watchdog group Citizens for Responsibility and Ethics in Washington, which sought logs of visits by executives of coal companies.

CREW is filing a lawsuit today against the Department of Homeland Security, which oversees the Secret Service.