A quick explanation "what the heck is going on" with the recent "contempt of congress" and executive privilege issue in our congress, for those of you who are curious but not keen to pull together what you need to know from various sources.
The original material behind all of this is over something called 「Project Gunrunner」, started under BushJr and continued in the Obama administration, which was intended to deal with gun trafficking between the United States and Mexican drug gangs; the program intended to track the structure of the gun trafficking networks, otherwise resistant to tracking efforts so far, by selling marked guns and noticing where they ended up. The programme was not particularly effective, it was done with no cooperation or informing of the Mexican government (perhaps for good reasons given issues with corruption), and a number of the marked weapons ended up escaping the view of the programme, and some of them were used to kill people. It's been widely considered not to have been a very well-concieved programme; I take no position on that.
In the last year, this has become very public and has been widely criticised, and recently became an issue that Republicans in congress have used to attack the Obama administration. Darrel Issa (Republican, chairman of the powerful House Oversight Committee) has been investigating this, using the death of one government agent in a gunfight with mexican gangs armed with weapons from the project as a flag.
Eric Holder, responding early to congressional criticism, indicated that he had just heard of the programme a few weeks before, a claim that seems to be inaccurate given records of his being briefed on it not long after taking office; later clarifications claimed that his knowledge of the details of the operation were cursory.
Recently, after receiving significant-but-incomplete documentation from Eric holder, Issa has pressed for release of the remaining papers. Holder has refused to do so, claiming that they pertain to ongoing operations that would be compromised by such release; this may be true, or it may be that the remaining papers suggest deeper administration knowledge/approval of the operation, or possibly both. Remaining details also may be more politically sensitive (e.g. showing high Mexican official involvement in gun smuggling, but NOTE: this is pure speculation on my part). Backing up Holder's refusal to release the documents, Obama has invoked executive privilege on those materials, a (normally reserve) power of the executive to resist the other branches on certain things it wants to keep secret for matters of national security (and similar); it's not a wery well-defined power, and it only saw rare use until modern times (Clinton and BushJr both used it on a number of occasions).
In response, a panel in the Republican-controlled house has nominated Holder to be held in Contempt of Congress, another reasonably-rarely ill-defined power of a government body. The vote on this will be held soonish if neither party backs down.
Both of these ill-defined powers being used against each other on this issue may lead the United States (in my relatively uninformed legal reasoning which you probably should not depend on if you have access to someone who actually has gone through law school) to a constitutional crisis; an actual charge of contempt of congress would require Eric Holder (as Attorney-General) to create a panel to decide the matter, an act that many legal theorists (see Unitary Executive Theory) believe cannot be done against a member of the executive branch of government, made more thorny yet because Eric Holder would be the target of the panel he would be (theoretically) structurally obliged by his role to convene.
Again: IANAL, so please consider the legal analysis included here possibly underinformed. Hopefully it's helpful for those of you who may have been following this and are more confused than I am on it.