There's a couple of factors there. It will depend on the reason for the dismissal, and whether he can be considered as having been responsible for making himself unemployed. He could face up to 9 week disqualification from Jobseekers.
This is a tricky area and he should probably speak to someone directly. The Irish National Organisation of the Unemployed run a free advice line on 01 856 0088 and would be familiar with this area.