After the Secret Service closed the investigation into the cocaine issue in mid-July, the Heritage Foundation filed a Freedom of Information Act (FOIA) request seeking the list of hundreds of individuals who may have accessed the area where the substance was found. In a July 25 letter (pdf) from the Department of Homeland Security (DHS), the agency denied the request.

"As your request seeks records reflecting visitors or related information concerning the Office of the President, please be advised that these records are not Secret Service agency records subject to the FOIA."

"Rather, these records are governed by the Presidential Records Act … and remain under the exclusive legal custody and control of the White House," the letter argued.

The DHS' response to the FOIA request made The Daily Signal, a news outlet of the Heritage Foundation, suggest that the Secret Service may have "never created such a list in the first place."

Steve Bradbury, a distinguished fellow at the thinktank, dismissed the DHS arguments for not turning over the visitor list, pointing to the legal difference between an agency record and presidential record.

The distinction is usually based on "who generates the record and whose business the record reflects," he told the outlet. "If it's an agency record, it's subject to FOIA. If it's a White House record, it's covered by the Presidential Records Act."

Mr. Bradbury said that the key question is whether the Secret Service used the White House logs to create its own new record.

If the Secret Service did use the White House records to create a "new document on its systems, which was its own list of suspects that it generated, that new document should" come under FOIA, he said.