Musannaf Ibn Abi Shayba 9:303

Sahl ibn Yusuf narrated to us, from ‘Amr, from al-Hasan, that he used to not grant the executor (*wasi*) any authority in the matter of marriage, unless he had said, "You are the executor regarding the marriage of my siblings." If he did that, then the executor is more entitled than the guardian (*wali*). Otherwise, the guardian is more entitled than the executor.