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Under the statutory scheme established by the PRA, the decision to segregate personal materials from Presidential records is made by the President, during the President's term and in his sole discretion, see 44 U.S.C. § 2203(b)
https://fingfx.thomsonreuters.com/gfx/legaldocs/dwvkdwkwdpm/frankel-judicialwatchvNARA–ABJopinion.pdf