From what I have heard over the years, hospitals still require arrt certification to work there due to hospital laws. It is the outpatient private facilities that can use other people who aren’t licensed to take x-rays. Correct me if I’m wrong though.

Yes, when the state doesn't recognize the RT (or those of us in imaging) then it is open practice with/without ARRT certification.  

Imaging centers tend to follow different guidelines than hospitals; Their supervision or credentialing processes aren't the same as a hospital.

Hospitals blanket credential the imaging professionals using the ARRT/ASRT as the hiring curriculum. Hospitals are tasked with determining the supervision requirements and job duties to better fit what their patient population needs are (this is in their bylaws). When there is no state law, they do still have the ability to hire uncertified Imagers and limited scope; if they were to choose to do so. (Billing would be a hairy topic and is in a league of it's own with this).

So, state laws/local requirements can determine how they hire, who they hire, and how they get reimbursement.  Laws keep the checks and balances there!  when there is no law, there essentially is no checks and balances.