The Department of Justice is deeply reluctant to brief House Intelligence Committee Chairman Devin Nunes, R-Calif., on the full details of a human agent who has provided intelligence to special counsel Robert Mueller's investigation of Russian interference in the 2016 Trump presidential campaign.

The basic concern is that such a briefing would jeopardize the source's cover and destroy their ability to conduct future intelligence operations. The DOJ also fears the individual's personal security would be put at significant risk by such publication.

The other concern here is what the intelligence community calls a dissemination or handling caveat. That's because disclosing the full array of information sought by Nunes would also necessarily entail breaching a Top Secret UK-ORCON or "originator control" handling that prevents the DOJ from sharing certain intelligence without British government approval.

That approval has not be given in this case just as it will not be given in relation to other British intelligence concerns.

Is the DOJ right to take this approach, invoking an ally's involvement in intelligence gathering as an excuse to evade congressional oversight? Some will vehemently disagree, but I believe the DOJ — with President Trump's support — are absolutely correct to resist Nunes' push here. There is immeasurable U.S. equity in protecting the intelligence sources and methods of our closest ally. To breach the dissemination caveat would be to betray British intelligence officers and agents who have trusted the U.S. with their secrets and their lives. It would degrade the special relationship in a very personal way.

And unless and until the U.K. releases the caveat, the DOJ can only provide Nunes with redacted material that respects British concerns.

Still, this isn't just about the British. At least one other allied intelligence service has cooperated with the Mueller investigation in relation to Russian intelligence communication with Trump campaign in Europe. They did so not to undermine Trump, but to support an ally on a matter of shared concern: countering malign Russian activity.

In turn, were the U.S. to start breaking its handling responsibilities in relation to one ally's intelligence material, it would shred its credibility with many other allies. That would lead U.S. allies to restricting their future provision of closely guarded intelligence to the U.S., thus endangering our own security.