"House rules" are not legally enforceable unless they are incorporated into an actual written employment contract between you and the employer. Otherwise, if not in a contract, they only represent the employer's policy, which the employer may freely change or even ignore. Similarly, unless you have a written employment contract, you are an employee at will and may be discriplined, written up, or reprimanded or even demooted, suspended, or terminated at any time, for any reason, without prior notice. So what you describe is certainly unfair, but it is legal.