Final answer:
In a double sale, the owner of movable property is the first buyer who takes possession of the property in good faith and without notice of the prior sale. For immovable property, ownership is determined by land registration and title deeds.
Step-by-step explanation:
In a double sale, the owner of the property depends on whether it is movable or immovable. For movable property, the general rule is that the first buyer who takes possession of the property in good faith and without notice of the prior sale becomes the owner. This principle is known as the rule of 'first in time, first in right'.
On the other hand, for immovable property, ownership is determined by the rules of land registration and title deeds. The person who has the proper legal title and has registered it according to the applicable laws would be considered the owner, regardless of any subsequent sales of the property.
It is important to consult specific laws and regulations in your jurisdiction to have a precise understanding of the rules regarding ownership in cases of double sales.