Law / Can I take my son to Poland? My ex partner has sole guardianship. [12]

Hello.
I'm Irish and my ex partner is Polish. We have a 9 year old together.
We have split up 4 years ago.since then i got married and he is in a relationship.
I have another child. My husband and I want to move back to Poland as he has land and property in Poland. My ex partner is refusing me to take my son with me.

My ex partner is a very good dad to our son and I don't want to hurt anyone . Especially my son. My ex partner has sole guardianship which I agreed to.

If I up and go and take my son with me will the Polish Courts order the return of my son back to Ireland?
Keeping in mind my son's grandparents and family live 80km from where I would be moving to . So it not like my ex partner would have difficulties seeing his son .