Classified information comes in many levels. Operational details against a campaign against the cartel is probably amongst the information you need to be the very most careful with. People in the DOJ who have access to that kind of information get years of training, they only keep it in physical files in ultra secure facilities or ultra secure computer systems that are not connected to the outside world in any way. The DOJ never releases the names of anybody who has access to that kind of information. If you just hand it over to a Congressional committee, literally, unpaid 19 year old interns get access to it, and the cartel would know every one of their names because it is all public record. Congresspeople have no training, no secure bunkers to keep their files in, just normal office computers hooked up to the internet...
Now, some times information that highly secure has been shared with Congresspeople. For example, leading up to the Iraq war, Bush brought in one senator and one representative from each party to much more secure briefings on some of the most secret stuff. Obama brought in members of both parties on the Bin Laden killing. But, that is a VERY different thing than this. Who those folks are is carefully negotiated by the parties and the administration. They're usually moderates. They're people that everybody trusts. They often, if not always, have had a top security clearance in the relevant area previously for some reason or another because they were in the military or the DOJ or something previously. I mean, if you want to, say, send in McCain and Kerry to review the documents, I'd be totally fine with that.
But Issa is a whole different deal. He is not John McCain. He's a hothead. He's a Joe McCarthy. A scandalmaker. That's his schtick. Trying to manufacture scandals for the conspiracy nuts. Nobody trusts him, nor should they. Turning ultra sensitive information over to a guy like that would get a lot of people killed for no reason other than to fuel his headline grabbing spasm. And turning it over to a whole committee, that should never happen.
