I guess it depends on whether you think the rank was earned over the course of your training, then it can't be taken, or if you think that your rank was a privilege loaned to you because of the way you conducted yourself, then I guess it can be taken.
Its kind of both in my opinion. Your grade signifies a combination of time in grade and up to what point you have gotten with regards to the curriculum.
Different organizations place different associations between rank and conduct, however, as a general rule, there is a standard that yudanja are held to regarding personal conduct. So personal conduct, depending upon the school or organization can, I suppose, play a greater or lesser part.
I know that if one's rank is attained under false pretenses in some way, the rank issued is subsequently null and void in most organizations. Though of course, there is no way to stop the person in question from hanging their ill gotten rank on the wall.
Some time back in a converasation here, it was said by several, myself included, that rank means the most in the school where you train, less within the same organization, and nothing beyond that.
In an independent school, everyone knows who is in good standing and who isn't. If someone is expelled, it makes little difference if their rank is formally stripped or not: they cannot train there any longer. If they go elsewhere, they have, as Puunui put it, plantation dollars, and will need to be evaluated based on their skills and ranked accordingly.
Daniel