A ceremonial role
Re: The letter that made former Head of State cry
He signed the law because it was his Constitutional duty to do so.
The law was passed by the democratically-elected Parliament of Samoa (the People’s House).
To reject the law was to reject the voice of the people. The Head of State is not elected by the people. The Parliament is.
Therefore, the Head of State’s role is simply to obey the wishes of the People’s House because they are deemed to be the wishes of the People of Samoa themselves. The Head of State’s role is ceremonial; not political.
To refuse to sign the law would be him involving himself in politics. It is as simple as that.