Source of Congressional Power

In the United States’ system of government, there is a checks and balances system where power is shared by the executive branch, the judicial branch and the legislative branch. To a great degree the legislative branch (the congress) exists to provide oversight of the executive branch. In other ways, congressional power can be quite extensive as visible in a number of famous court cases where such power was challenged and the end result of the court cases resulted not in a lessoning of congressional power, but an affirmation and expansion of it.
Examples of famous court cases that involve Congressional power include McCullough vs. Maryland (the constitution grants Congress the ability to carry out the constitution when the function of the national government is concerned); South Carolina vs. Katzenback (the authority of Congress to pass the Voting Rights Act was upheld); Gibbons vs. Ogden (Congress’ powers under the Commerce Clause of the Constitution were upheld); and McGrain vs. Doherty (inherent powers defined)
Of all its powers, Congress is most notable for the ability to regulate and maintain interstate (and foreign) commerce, write tax law, declare war and fund the military, confirm nominations to the federal court and even impeach the President if he breaks the law (or opt to ignore the fact that he broke the law) While some may wrongfully argue that such powers lead to a long, bureaucratic process that could be much better served it were streamlined by a central authority, the fact that Congress prevents the emergence of a central authority is its greatest asset.

That is to say, by not allowing the executive branch to develop overreaching power, the Congress eliminates the President from emerging as a dictatorial figure who is not subject to oversight. If too much power is placed in the hands of any one branch of government, then the ability of the government to overreach and become corrupt is a very real possibility. Congress keeps this system of checks and balances in line. The expansion of Congressional power also exists to greatly help the people. For example, South Carolina vs.
Katzenback solidified the power of the Voting Rights Act and allowed people to maintain their ability to exercise their right to vote. The control of commerce as defined by McCullough vs. Maryland held businesses accountable and did not give them free reign to do whatever it is they wished at the detriment of society as a whole. Yes, there have been numerous complaints over the years that Congress has overreached its authority and regulated/interfered in business and private lives beyond what is appropriate; but such overreaching has been curtailed in the past when public outcry became loud and virulent.
As such, it would be hard to press a case that Congressional Power is abusive or overreaching since Congress does, ultimately, have to be accountable to its constituency every election cycle. Because of this, the ability to exercise power remains in check and can not overreach beyond what the population wishes. So, in that regard, congressional power is not unlimited and is subject to the same checks and balances system that the other parts of government are subject.