If this company is not an excluded company, per IC, it would be illegal for them to fire you. End of story. It does not matter if they train the police, if they train the Navy SEALs, or if they own the city. If you are fired from a company that is not excluded, by law you may sue for damages and legal fees. Show me otherwise and I will admit I am wrong, until then it's all illegal.
The company mentioned, that trains the PD, is excluded.