I suggest you read this summary on one of the best books in Political Science, a president is actually not as powerful as you think him to be, from George Washington to Trump:
"Effective influence for the man in the White House stems from three related sources: first are the bargaining advantages inherent in his job with which to persuade other men that what he wants of them is what their own responsibilities require them to do. Second are the expectations of those other men regarding his ability and will to use the various advantages they think he has. Third are those men's estimates of how his public views him and of how their publics may view them if they do what he wants. In short, his power is the product of his vantage points in government, together with his reputation in the Washington community and his prestige outside.
"A President, himself, affects the flow of power from these sources, though whether they flow freely or run dry he never will decide alone. He makes his personal impact by the things he says and does. Accordingly, his choices of what he should say and do, and how and when, are his means to conserve and tap the sources of his power. Alternatively, choices are the means by which he dissipates his power. The outcome, case by case, will often turn on whether he perceives his risk in power terms and takes account of what he sees before he makes his choice. A President is so uniquely situated and his power so bound up with the uniqueness of his place, that he can count on no one else to be perceptive for him" (150).
I actually read Neustadt in undergraduate! I really enjoyed his work. I totally agree that agencies do not act at the explicit direction of the president, and they definitely have a degree of discretion. However, that is a far cry from saying they are controlled by a party opposite to what controls the executive, and is not relevant to the legal element of probable cause needed to make arrests.
I suggest you read this summary on one of the best books in Political Science, a president is actually not as powerful as you think him to be, from George Washington to Trump:
"Effective influence for the man in the White House stems from three related sources: first are the bargaining advantages inherent in his job with which to persuade other men that what he wants of them is what their own responsibilities require them to do. Second are the expectations of those other men regarding his ability and will to use the various advantages they think he has. Third are those men's estimates of how his public views him and of how their publics may view them if they do what he wants. In short, his power is the product of his vantage points in government, together with his reputation in the Washington community and his prestige outside.
"A President, himself, affects the flow of power from these sources, though whether they flow freely or run dry he never will decide alone. He makes his personal impact by the things he says and does. Accordingly, his choices of what he should say and do, and how and when, are his means to conserve and tap the sources of his power. Alternatively, choices are the means by which he dissipates his power. The outcome, case by case, will often turn on whether he perceives his risk in power terms and takes account of what he sees before he makes his choice. A President is so uniquely situated and his power so bound up with the uniqueness of his place, that he can count on no one else to be perceptive for him" (150).
https://adambrown.info/p/notes/neustadt_presidential_power
I actually read Neustadt in undergraduate! I really enjoyed his work. I totally agree that agencies do not act at the explicit direction of the president, and they definitely have a degree of discretion. However, that is a far cry from saying they are controlled by a party opposite to what controls the executive, and is not relevant to the legal element of probable cause needed to make arrests.
The justice department works even more independently than, say, the dept of transportation. You know this.