Any provision of this subchapter held to be invalid or unenforceable as applied to any person or circumstance shall be construed so as to continue to give the maximum effect to the provision permitted by law, including as applied to persons not similarly situated or to dissimilar circumstances, unless such holding is that the provision of this subpart is invalid and unenforceable in all circumstances, in which event the provision shall be severable from the remainder of this subchapter and shall not affect the remainder thereof.