I was living with a man that I have asked to leave immediately. He does not pay rent, will buy a few groceries once in a while, buys gas when he wants to go to his hometown. His name is not in the rental picture as I am renting from a family member. He says I cannot force him out. I told him I would bring the sheriff if he did not go peacefully. He did leave but I am not sure if he can do anything about me asking him to leave. Need advise...

Laws vary by location. You did not provide your location so we are unable to help you specifically.

I live in North Carolina. What is the law re: asking a live in boyfriend to leave. He does not pay rent nor utilities. Buys some groceries which he helps eat, buys some gas when he wants to go visit his family in Greensboro, NC> I asked him to leave which he did. Did I break any law?

It depends on how long he lived there and if he claimed this his residence via mail, drivers' license etc.

Most likely you did break the law and should have served him with a formal eviction notice.

He was here only about 45 days. His name is not on any paperwork. I rent from a family member. He received no mail here.

He is a resident and would legally have to be evicted. There is nothing wrong in asking him to leave and if he did, then he is gone. You should now change the locks if he has moved out, but only if he has already moved out. If he did not move, you would have had to treat him like a renter (tenant) with official notice, and then to court to evict

NC law allows you to give eviction notice verbally when there is no lease.
It allows for termination of tenancy between 2 and 10 days when there is no or less than a 1 year lease.
Since you gave him notice and he left, you did nothing wrong.
He can't do anything now (unless he left his possessions behind as proof that he still lives there). He could have refused to leave and made you go through court to evict.

...
Most likely you did break the law and should have served him with a formal eviction notice.

Incorrect. OP asked him to leave and he left. Absolutely nothing wrong with that.

Whether he was, under the law in OP's state, a tenant or not (and thus whether he could have been legally "ousted" as the law generally calls such things as changing the locks, etc.) is thus a moot point.

Here is the bottom line, You cannot physically force someone to leave your home. You have every right to request that they leave. If they refuse then you have to use legal means to remove them. What those legal means entail depends on how long they have been there, whether they have established residency, etc.

Since he did move voluntarily, then you are in the clear.