Stealing from the party - Chaotic Neutral or Neutral Evil?

All in the title. Just played a game with a friend Dming and one of his other friends joined us (btw we have already played a few sessions without that friend and everything went fine). But that new guy is playing a Chaotic Neutral goblin who keeps trying to steal from the party and "claims" first dibs on the loot. I try to tell them that is a Neutral Evil alignment because he is putting his wants first at the cost of the party and won't see reason. But they say is Chaotic Neutral, then I say that Chaotic Neutral is going with the flow and what you feel is right. Not actively trying to better yourself from stealing from the party.

Which one is it?

Edit: to clarify, the player was trying to steal magical items and "claim" loot that he probably couldn't even use.