Somehow I missed this when it came out, in November.
Apparently there's been serious debate in the U.S. State and Defense Departments over whether the U.S. should share permissive action link (PAL) technology with Pakistan.
For background on PALs, see here and here.
It seems that this would be a good step towards improving Pakistan's nuclear security. The U.S. itself has not always been exemplary in this area: for a very long time, weapons on Navy submarines did not have PALs.