Or a more likely case is that Trump knows if he orders the release, they will not follow the order. That would weaken Trump considerably if it is shown he has no control over the executive branch. Sure, a bunch of us will be pissed off. But in the end, congress will support the deep state over Trump every time.
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President Trump doesn't seem like the type of person who enjoys loosing. Nor the type who would take it relatively well being embarrassed like that.
If such a scenario played out, I wouldn't be surprised if he ordered the federal marshals to go in an seize the material.
Now, if they refused, who is left that would take orders from POTUS?
I would fully support Trump ripping the lid off and exposing a Constitutional crisis. The sooner, the better.