Can I be fired for violating a policy that is not clearly stated in the handbook and has never been enforced before?

I called off work for a few days due to illness.Our work handbook states that if you take consecutive days off work due to illness and bring in a doctors note it will only count as one point for the whole leave instead of one point per day. When I brought in my doctors note yesterday, I was told it only excuses one day because the note did not exempt me for each individual date that I was absent. I have done this twice in the past and brought in a note that only excuses the one day I visited the urgent care and been given one point for all of the days I was absent. I even have copies of the doctors notes from the past. No changes have been made to our handbook and my work is saying this policy has never been changed. But because of the extra points I am unjustly receiving I am now fired. Is this legal?