Family trust vs. POA- does sister's husband have the authority to access bank accounts if she is POA?

Before my dad died he put all Bank Account monies into a Family Trust. My sister and I (are names) are included on the Family Trust. My sister has POA but her controlling husband is trying to access and control the Bank Accounts on behalf of my sister. He controls her and tells her what to do. She does not speak up for herself. Question - can her husband even though he does not have POA but my sister does - does he have the authority to access the Bank accounts? She allows him to because she does not say anything because he controls her like a little puppy dog?