Loudspeaker A320

[Boyington]

On the A320 why is it that Loudspeaker U/S on Captain side is a' No Go' item but a 'Go' item on the First Officer's side?

[BBH]

I suppose it is due to EMER ELEC configuration as every R/NAV item needs to be operative on CM1 side.
Same rule for most of acft I have flown.