Separation of powers is one of the most vital principles that do undergird the American government system. This describes the parceling out of functions of government, authority and power to different institutions that possess relative independence in the federal system. This will help to prevent any institution from being controlled by any authoritative system. Each of the branches has a set of inbuilt checks and balances in the constitution to ensure that there is sufficient legal weaponry for each branch to be able to protect itself from possible bureaucracy. This will also avoid encroachment by other branches to its independence. This power allows some branches to say no to some decisions that are made in the field of specialization of the respective branches.
An agreement may be reached upon by two houses of congress to compromise or pass a law but at the same time, the president can choose to veto it. On the other hand, the president and congress may come to an agreement to pass a law but upon the federal judiciary declaring it to be unconstitutional, courts would then refuse to accept the law as being enforceable. Courts may issue certain prohibitory and mandatory injunctions to persons including officials holding public positions. This may not automatically happen since the power of the law enforcement agencies will be needed to enforce it in case the persons choose to disobey the injunctions. This check is effective because of the jealousy that does exist mostly between the president and Congress. The ambitions that exist also are able to make these checks successful.
Congress cannot on the other hand control the outcome of a given ruling in a particular case. However, Congress has the authority to both set-out and redefine the mandates of various courts of the Federal State. The president has his powers also put in check. The president who possesses the power to supervise the behavior of military and foreign policy must seek ratification by the senate before their enforcement. At the same time, only Congress can appropriate public money to offset such costs as the dispensation of foreign aid. Under this system, a branch may have primary authority in the decision-making of certain issues but will also require minimal voluntary participation of other branches if the successful implementation of the initiatives is to be realized.
A weakness that exists is that the Congress and the Executive branch are mostly controlled by the same party and so collusion is mostly realized. The checks that the Senate has on the president may not be so effective if the president has a majority of his members in the senate since they will tend to sympathize with him. The rivalry between the Judiciary and the presidency will ensure the effectiveness of the checks and balances.