This argument is predicated on one's following the Orthodox view of Judaism. Under any other view, this position is wrong (but there is no place to comment about the presuppositions of any position or topic so I'm putting it here).
If one accepts Orthodoxy's view, that the law exists and all who are Jewish are bound by it then there is nothing in life under that law which makes its application dependent on the will of the individual. If you are a licensed American citizen driving a car, then whether or not you want to obey the speed limit, you "have" to (with "have to" simply meaning "required to under threat of a penalty by an authority to which your membership indebts you").
If you are not Orthodox and feel either that the law is a function of personal will or that the authority is not authoritative, then one does not "have to" in the same sense.