With the "or", you have equal rights to possession of the vehicle, regardless of who paid for what. You can sell the car without the buyer's consent. You can transfer the title to yourself alone. I suggest you stop thinking of the other person as the "buyer". The car was sold to the both of you. You are as much a buyer as the other. You are as much the owner as the other.
Law enforcement should not be concerned.
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You are legally free to use the car as you wish, as long as its not for an illegal purpose. However, the other individual you refer to can assert an equitable lien against the car to the extent of their contribution.
No, you cannot be arrested for driving the car when your name appears on the title, and it is properly registered and insured. If the other co-owner attempted to report that you have stolen the vehicle, they would be filing a false police report.
Yes, you can sell the car without the other co-owner's consent if the title reads: "Owner A" OR "Owner B" but remember, the other party can just as easily sell the car "out from under" you without your consent!
You are in a sticky situation, the two of you created. There are ways to disentangle this situation, but it will involve transferring title, and paying-off and/or refinancing the current loan.
I am an attorney who is only licensed in the State of Florida. My answer is general legal advice based upon what I perceive your question to be, and should not be relied upon because every person's facts and circumstances are unique, and because specific laws vary from state to state. To completely evaluate a legal issue requires reviewing and evaluating all relevant facts, applicable laws and other information. My answer does not create an attorney-client relationship, and offered for informational purposes only.