Article 1, Section 8, clause 18 of the United States Constitution gives Congress power to make any laws considered "necessary and proper" for the nation. According to Wikipedia, this clause, often called the "Necessary and Proper" or the "Elastic" clause, is sometimes accused of giving too much power to Congress.
Article 1 of the United States Constitution lays out the organization of Congress, its houses, and its duties. As enumerated by the University of Missouri-Kansas City School of Law, the 18th clause in Section 8 lists powers that Congress possesses, such as levying taxes, creating a currency and building roads. The 18th and final clause accounts for any not mentioned by giving Congress to the power to make any "necessary and proper" laws needed. According to Wikipedia, the intention of the Necessary and Proper Clause is to make sure that Congress can create laws that will enable it to exercise powers in the interest of the country.
In Federalist Paper no. 44, future president and one of the authors of the Constitution James Madison acknowledged that the clause was opposed by many. However, he argued that it was necessary for the government to have power to put into effect laws that they had not already thought of. According to Wikipedia, clause 18 was a correction to the lack of power afforded by the previous Articles of Confederation.