Investigation of misconduct in those two agencies appears to differ from the manner in which the Inspector General handles oversight of other agencies within Homeland Security. In a Dec. 16, 2009 memo, written to U.S. Customs and Border Protection, the Inspector General took issue with efforts by that agency's internal affairs division to investigate misconduct by its own Border Patrol agents.
"The Office of Inspector General is the organizational element within the U.S. Department of Homeland Security that is statutorily responsible for conducting and coordinating all investigations of suspected criminal wrongdoing by DHS employees, and has specific oversight responsibility for internal investigations performed by components," asserted Thomas M. Frost, then the assistant inspector general for investigations, in the memo.
Grassley said he believes the approach should be the same in the case of alleged Secret Service misconduct.
"The Inspector General should take a more active role because we can't be left with any questions that the protection of the President and national security are at risk," he said.
Grassley has also engaged in a war of words with the Obama administration over its handling of his question about the possibility that any White House advance staff joined in the partying in Colombia that occurred in advance of the president's arrival there.
Press Secretary Jay Carney said the White House Counsel's office conducted its own internal review and concluded no White House staff had participated. Grassley has sent the White House a letter asking that the details of its internal review be made public.
The Inspector General's office told ABC News it has not deviated from its standard procedure in this case. And Napolitano told senators she has "full confidence" in the Secret Service's ability to conduct its own internal review.
"Director Sullivan has the President's and my full confidence as this investigation proceeds," she said. "The investigation will be complete and thorough and we will leave no stone unturned."