As a co-buyer on an automobile, can the other party take full possession? Both parties names are listed as the Purchaser's. Only one purchaser signed the retail order for the motor vehicle, and if so, how can one become a no co-buyer?
Your question about full possession is a little ambiguous. As long as both names are on the title then both people are entitled to the use of the automobile. If you have a copy of the keys, then you are legally entitled to drive the car. Even if the other owner reported it as stolen, you are on the title, so you have a legal claim.
Most states recognize the and/or rules on the title. If the two names on the title are joined by the word AND, then both parties are required to transfer or otherwise dispose of the vehicle. If the two names on the title are joined by the word OR, then either person can sell the car without involving the other. Other legal questions about whether you could sue for half of the money if one sold without the other's consent can't be answered except on a case by case basis.