No, it's not illegal discrimination, giving rise to a cause of action:1) Height is not a protected category (the main categories are race, sex, religion, age over 40, disability), and companies may take into account--i.e. "discriminate" legally--on any basis except the specifically protected categories. This is THE big stumbling block--you're not protected on the basis of your height.2) Even in regards to the protected categories, a company take into account job needs: e.g. a woman wouldn't be hired as a mens room attendent in a hotel. If there is a legitimate issue about your ability to do the job (drive) on account of height, then even if height were protected, that might be enough to allow them to not rehire you.