Sections 12.1-16-04 through 12.1-16-06 do not preclude the use of medications or procedures necessary to relieve a person's pain or discomfort if the use of the medications or procedures is not intentionally or knowingly prescribed or administered to cause the death of that person. In addition, sections 12.1-16-04 through 12.1-16-06 do not preclude the withholding or withdrawal of life-prolonging treatment pursuant to state or federal law.