Nothing in this subchapter may be construed as prohibiting any private person, Federal agency, or State agency from engaging in standards-related activities that do not create unnecessary obstacles to the foreign commerce of the United States. No standards-related activity of any private person, Federal agency, or State agency shall be deemed to constitute an unnecessary obstacle to the foreign commerce of the United States if the demonstrable purpose of the standards-related activity is to achieve a legitimate domestic objective including, but not limited to, the protection of legitimate health or safety, essential security, environmental, or consumer interests and if such activity does not operate to exclude imported products which fully meet the objectives of such activity.