Did he get his citizenship? If he did, then no problem.
If he did not he is still technically a PR, however, getting to the Canadian border is going to pose a huge challenge for him because I suspect he does not have a valid PR card, he would need to apply for a PRTD which in all liklihood would be denied and steps would then be taken to revoke his PR status. If he can get to the US, then he MIGHT be able to slip past the land border without being reported. If he does this, he can lay low and not apply for anything from CIC for at least 730 days which will bring his RO back into good standing. If he gets reported at the border, he can likely expect they will revoke his PR and ask him to leave the country.