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It depends on which program he was read into I think.
I don't know and I doubt it will be easy to find which programs he was read into and which programs covered the TSP. I think you sign something when you get read into each individual program saying you won't disclose any information shared about the program you are being read into and if you do its punishable by law.
I am not a lawyer nor very familiar with the laws governing these things, these are just my vague recollections of what I was told when I was given a TS:SCI clearance years ago.