Restricting the label protects the consumer from false advertising. Truth in advertising is important to the consumers, and companies should not be allowed to misrepresent their products. The buyer has a right to know if part of a product is not made in the United States. If manufacturers are allowed to use the label despite the truth, then the label becomes ambiguous. Some manufacturers will argue that having their products made entirely in the United States is impossible.
Nothing is impossible.
Many companies make it happen by finding innovative solutions to the problem. An example of this is the Converse shoe company. They make a Chuck Taylor All Star, and it is manufactured entirely in the United States. These companies should be rewarded, not ignored. Trust in a company and its product is dependent upon this label.