my friend left to return to Canada, in January, he stayed longer than 6 months in the US, with only a passpor?

[bw022]

What do you mean? Nothing happened to him. He returned to Canada.

There is no law against a Canadian entering Canada. Nor is there any controls in the United States on people leaving the country. Canadian Border Services Agency will scan his passport and he'll be in Canada.

If it tried entering the United States again, then something will happen to him. USCIS and CBSA exchange information and upon attempting to re-enter the United States USCIS will see that he entered the US on X date and didn't re-enter Canada until Y date. They can quickly see that he failed to leave the US within six months. He would be stopped, asked questions, asked about why their records show him in the US for more than six month, etc. and finally they'll likely deny him entry into the United States again.

If you want to find out what happened to him... why don't you call him, email him, look him up in Facebook, try a phone book, ask other friends for his contact information, etc. If he didn't give you his contact information... then he isn't much of a friend.