(a) Nothing in this subchapter shall impair or supersede any legal right or legal responsibility which any person may have to effect the withholding or withdrawal of life-sustaining procedures in any lawful manner. In such respect the provisions of this subchapter are cumulative.
(b) This subchapter shall create no presumption concerning the intention of an individual who has not executed a declaration to consent to the use or withholding of life-sustaining procedures in the event of a terminal condition.