The Constitution of the United States of America explicitly states the five fundamental functions of good government yet Congress ignores them, the Supreme Court ignores them, and to date, the Presidency has ignored them countless times. In order for legislation to be deemed "constitutional" said legislation must not violate the mandate established within the preamble to wit
"establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity"
Clearly, international trade is important to our nation. Equally so is that the trade agreements we establish must adhere to all five of the aforementioned principles.