I think the original question was asking a question about being. Clearly one can call yourself anything you want (as long as there is no intention to defraud). But surely the question means is it legitimate for me to describe myself (to myself and/or others) as an Instructor ?
Quoting the Law, FARS or any other legal prose is completely missing the point. In Malaysia they have just brought out a new requirement in the State of Selangor that requires you to have a licence to teach Islam but that is just a control mechanism.
On a fundamental level an Instructor is a Teacher or Guru. Once s/he has reached that level (like 1st Dan in Karate) s/he will always be a Teacher. S/he may lose their licence to practice but s/he is still a teacher.
And to former students s/he will always be their Guru.
