In Scrum, the Product Owner is responsible for maximizing the value of the product resulting from the work of the Development Team. One of the primary ways the Product Owner does this is by managing the Product Backlog, which includes clearly expressing Product Backlog items, ordering the items to best achieve goals and missions, and ensuring that the Product Backlog is visible, transparent, and clear to all. This means that the Product Owner has the final authority on the order of items in the Product Backlog, as they are best positioned to understand the strategic and market value of the work to be done.
References: The Scrum Guide and the Professional Scrum Product Owner™ (PSPO I) study materials, specifically the sections on 'Managing Products with Agility' and 'Understanding and Applying the Scrum Framework', which outline the accountabilities of the Product Owner in managing the Product Backlog