This is an interesting question, and one to which the answer does not seem to be agreed upon by all Taekwondo practitioners. In this post I will give my opinion.
I generally believe that if you have achieved the level of black belt in Taekwondo, that you remain a black belt even if you stop training in Taekwondo. I also believe that you retain your degree of black belt – i.e., if you are a fourth degree black belt, and you stop actively training in Taekwondo, you remain a fourth degree black belt, even if you don’t train for several years. (However, I believe that if you are a colour belt, and you stop training for several years, you do not necessarily retain your grade.)
There are many people who disagree with this point of view, arguing that if you are a black belt, and you stop training for several years, you will then no longer be able to do what a black belt Taekwondo practitioner can do – and should be able to do. A black belt should be an indicator of a certain level of ability, and if, through not training for several years, you lose the level of martial skill required of a black belt, then you should no longer be a black belt in Taekwondo.
However, if we were to revoke the status of those people who no longer have the level of skill required of a certain degree of black belt, this would cause some problems. For example, perhaps someone trains in Taekwondo for fifty years, starting at age 20 and finishing at age 70; they reach the level of grandmaster, but at 70, for health reasons, they have to retire from Taekwondo. Should such a person no longer be considered a ninth degree black belt and a grandmaster because they no longer retain that level of skill? It is generally the precedent in Taekwondo that such a person would be a ninth degree grandmaster for the rest of their life (and may even be promoted to tenth degree (in some organisations) posthumously). It would seem evident from this example that in Taekwondo a person’s degree is not revoked when they stop training.
But let’s consider a different example: consider someone who starts training in Taekwondo at age 20, and at 25 becomes a black belt. Upon becoming a black belt, they then quit Taekwondo altogether. By the time such a person is 50 or 70, are they still a black belt in Taekwondo? To say that they are might seem preposterous – by the time they are 30 they will have already not been doing Taekwondo for as many years as they were training in it. By the time they are 50, they are very unlikely to have retained much of the skill that they developed.
However, even in this second example, I would say that such a person still retains their status as a black belt in Taekwondo. A belt in Taekwondo is primarily a symbol of what you have achieved, and secondarily an indicator of your current skill level. And someone who has achieved black belt in Taekwondo, but who hasn’t trained in it for a long time, and who no longer has the level of skill required of a black belt, will be aware that they are no longer at that level of skill. Such a person probably should not go around saying ‘I’m a black belt in Taekwondo’, as this implies currency. However, they are, in my view, technically still a black belt. And this is, I think, the convention followed by the vast majority of Taekwondo organisations around the world.