It is up to your employer whether or not to permit this. There is no legal requirement that a company allow a worker to revoke a resignation. Basically, if you are an "at will" worker, your employer can set the conditions of the workplcae much as it see fit. Accordingly, unless denying you the right to revoke your resignation violates the terms of an employment contract/union agreement or in some way constitutes some form of legally actionable discrimination, you have no claim here.