If the attacker forms a chain with higher chainweight, checkpoints won't hinder or help the reorg.  That higher weight chain will replace all instances of the current chain, regardless of if they have checkpoints enforced or not.  The only way to use checkpoints in an attack is to block the checkpoint server from the open internet.  The thing is, it's near impossible to find the IP address of the checkpoint server, because checkpoint authority is based on a cryptographic signature rather than an IP address.