• The "Elastic Clause" of the Constitution grants Congress power to pass unspecified laws "necessary and proper" for the exercise of its expressed powers
• Implied powers have often been controversial
• Over time, Congress's powers have grown as more and more kinds of government activity have been accepted as implied powers

This last power is enshrined in Article I, Section 8, Clause 18—one of the most important and controversial clauses in the entire Constitution. This "Necessary and Proper Clause" (sometimes also called the "Elastic Clause") grants Congress a set of so-called implied powers—that is, powers not explicitly named in the Constitution but assumed to exist due to their being necessary to implement the expressed powers that are named in Article I.

But what the heck does that mean, exactly?

We know that Congress has the power to regulate interstate commerce. (It says so right there in Article I, Section 8, Clause 3.) But does Congress have the power to, say, make a rule setting a national minimum wage? Is that minimum-wage law really "necessary and proper" for Congress to exercise its authority to regulate interstate commerce?

Today, most people would say yes. We do have a national minimum-wage law, and very few people now argue that the law should be considered unconstitutional. We interpret the commerce clause pretty loosely, assuming that Congress has the legitimate authority to pass all kinds of economic rules and regulations as a "necessary and proper" part of exercising its broad commerce powers.

But this wasn't always the case. Throughout the late nineteenth century and well into the 1930s, the Supreme Court insisted that such laws were unconstitutional, that they were not a "necessary and proper" part of regulating interstate commerce at all and thus the government had no right to enforce them.

What changed? Not the Constitution. But our understanding of what's "necessary and proper" today simply isn't the same as what it was a century ago. Now you can see why Article I, Section 8, Clause 18 is sometimes called "the Elastic Clause"—the definition of "necessary and proper" can be stretched pretty far in one direction or the other, depending upon the dominant political trends of the moment.

And because the definition of "necessary and proper" is so subjective, the implied powers that derive from the Necessary and Proper Clause have often been extremely controversial and subject to ferocious political disagreement. And this has been the case since at least George Washington's presidency, if not even before.