Bowsher v. Synar
The president signed a law that tries to eliminate the budget deficit. It calles for the Directors of the OMB and the CBO to calculate the necessary budget reductions. The Comptroller General then has to review the reports and then report his conclusions to the President. The president must then issue a sequestration order which Congress must legislate on. The act has a fall back provision in the case the original provision was found to be unconstitutional; basically the Controller General was left out of the process and budget cuts are reported directly to a Congressional Committee.
Synar, a Congressman who opposed the bill sued in Federal District Court. The Court ruled that the Act survived a delegation doctrine challenge but the role of the Comptroller General violated the separation of powers doctrine.
The court rules that the president appoints officers of the United States but when the appointment is made and confirmed, the only way Congress can remove the officers is via impeachment. If Congress had the power to remove him, then this would be able to influence him, and control his functions. To permit the removal would be like permitting the legislative veto (which was disallowed in Chanha).
The Court then argues that the Controller General is actually a member of the executive branch. The court rejects the dissent's argument that the CG is "essentially ministerial and mechanical" in his actions. Rather the court says that he has the ultimate authority to determine the budget cuts to be made, and therefore his authority is highly executorial.