If a PO's behavior results in a poor or improper implementation of Scrum, then the Scrum Master may need to work with the wider organization in order to tackle this impediment. This could mean approaching stakeholders directly and appraising them of the situation, including any risk to delivery or the potential impact on return on investment.
That said, the Scrum Master should always try and resolve the matter with the PO in the first instance.
That would also be my first approach and it seems logical. However, there was a question in the PSM 1 yesterday that made me choose 2 answers. I also selected that the SM could address the problem with the PO's functional managers.
However, not being able to reproduce the exact question and the possible answers, I'll never know.