Demand MVA Refund Prorated Registration on Return Tags

We are required to pay for multiple years for a vehicle registration. Why and how is it legal for MVA to refuse to refund any prorated amount, unless there are 12 months remaining on the registration? I just returned some tags from a vehicle I sold and had almost five months remaining and I don't get a prorated refund? This is nothing less than an abuse of power, it should be illegal, and it is absolutely immoral.