Unless it's in a text of law, it's not legitimate.
This is not correct. There's always some degree of ambiguity, and as the Courts hear cases that test those ambiguities, those precedents -- known as "case law" -- effectively become part of the law, even though they're not in the text.
Very very incorrect. See http://en.wikipedia.org/wiki/Case_law and http://en.wikipedia.org/wiki/Common_law , which have the force of law but are neither statutory nor regulatory law (which I assume is what you mean by “a text of law”; arguably case law, since it is in the form of written decisions, actually is “a text of law” anyway).
This is not correct. There's always some degree of ambiguity, and as the Courts hear cases that test those ambiguities, those precedents -- known as "case law" -- effectively become part of the law, even though they're not in the text.