Can the Treaty Power Infinitely Expand Congress’s Power?

To quote Nicholas Quinn Rosenkranz, “[t]he most important sentence in the most important case about the constitutional law of foreign affairs is this one:”

If the treaty is valid there can be no dispute about the validity of the [implementing] statute under Article I, § 8, as a necessary and proper means to execute the powers of the Government.

The practical effect of this sentence is that the treaty-making power automatically gives Congress the power, when necessary, to pass legislation to give a treaty domestic legal effect even if Congress could not pass such legislation on its own.  In other words, Congress can do through implementing legislation what it otherwise could not.

What makes this scary, in theory, is that the limits of the Executive’s treaty-making power under Article II have not been defined by the Supreme Court.  While we know that there has to be some limit to what the President may impose upon the country through international agreement, we don’t know exactly where that line falls.  Nobody would argue that the President could renegotiate the slave trade under the guise of treaty-making and thereby nullify the Thirteenth Amendment.  But there are certainly less problematic examples.

The issue surrounding implementing legislation, however, is more subtle.  Congress’s powers are limited and articulated piecemeal in Article I, section 8, the most significant of which is the authority to regulate interstate and foreign commerce.  So if the President negotiates a treaty that requires implementing legislation, the subject matter of which falls outside the scope of Congress’s express powers, the above language by Justice Holmes means that Congress can nevertheless pass such legislation.

Examples of a problematic expansion of Congressional power under this theory need not be as abhorrent as nullifying constitutional rights.  The reach of Congress’s regulatory authority calls into question basic federalist principles.  The greater Congress’s regulatory terrain, the smaller becomes that of the States.