passport validity for Irish

I have an Irish passport holder going to hong kong in december 2011 returning on 04 jan 2112 the passport is valid until march 2012 am I correct to say that if the passport is valid out and back then he can travel there is no rule that says it has to be one or two ...or 6 months valid after return date like some contries have?
Also he will not require a visa
Thanks
John