Obstruction of justice?

I am not a lawyer, and most of what I learned about the law has come out of the television. But in looking at the shocking account in the New York Sun of FBI investigations into leaks from intelligence agencies that have been "stymied" by a lack of cooperation from the unidentified "victim agencies", I am scratching my head and wondering whatever happened to charging uncooperative people with obstruction of justice.
In January 2005, a top FBI official asked the Justice Department to close three pending leak inquiries because the "victim agency" repeatedly refused to assist the probes. The FBI's contact at the agency "has been uncooperative with the investigating field office and on numerous occasions failed to return phone calls or provide the case agent with requested documents pertinent to the investigation," the memo said, adding that the agency "cancelled personnel interviews, security briefings and meetings at the last minute and failed to reschedule for another time."

"None of the cases can proceed without the cooperation of the substantive unit at the victim agency, therefore the FBI considers all logical leads covered," the FBI official wrote. Within days or weeks, the cases were closed.
Keep in mind that the offenders, the leakers of documents, are members of the "victim agencies." If they are allowed to deep-six investigations into their crimes, then the law has become a joke, and we have had , in effect, a partial coup de etat in our intelligence service(s).

Perhaps a legal authority can explain to me why someone who repeatedly refuses to cooperate in an investigation is not charged with obstructing justice. I thought that potential penalty was how investigations got cooperation.

Even if charges are not brought, why hasn't the Bush administration fired those who failed to cooperate? What am I missing?
 
Update: Macsmind has an informed take and draws on a lawyer at Powerline:

Scott at Powerline asks:

"This story needs to be read in conjunction with DOJ's failure to pursue Sandy Berger more vigorously. Many people are expressing puzzlement over why a Republican Justice Department would allow these investigations to fizzle out. The question I would ask is whether DOJ is any more "Republican" than the State Department or the CIA."
I've got that answer for Scott, it's more than 2-1 liberal democrat in the lower echelons of the DOJ as it has been throughout time. Much as the Department of State, CIA, etc. While administrations can place their own at the top, a lot of those who dwell within are holdovers from previous administrations.

Note that party affilitation doesn't make a prosecutor, lawyer or cop dirty, nor necessarily without influence, yet politics can do come into play and thats a fact. Remember Washington is in many ways a board game. Let's just hope that the fools that sometimes play don't cause us all to lose in the end.
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