I am an adult, and this past January moved back in with my father. He rents a house, and is the only one on the lease. We never discussed an amount for rent or anything regarding money. He has been allowing me to live with him so I could get back on my feet. Tonight when I got out of work the lock was changed, but he let me in. He told me I have to leave in the morning or he will call the police and have me removed. Can he do that or does he have to evict me? I live in NH.

Probably not. You have been living there as your official address for a few months. He can't just kick you out without notice. Unless you live in a small town, the police are not likely to get involved unless there is violence reported.

You can tell your father that he needs to give you 30 days notice and he needs to give you a new key. Otherwise he will be guilty of an illegal eviction (see Illegal Eviction Procedures in New Hampshire | Nolo.com (http://www.nolo.com/legal-encyclopedia/illegal-eviction-procedures-new-hampshire.html))

As long as you can show the police proof that you have been living there as your official residence, they should be on your side if they do come.

....

You can tell your father that he needs to give you 30 days notice and he needs to give you a new key. Otherwise he will be guilty of an illegal eviction (see Illegal Eviction Procedures in New Hampshire | Nolo.com (http://www.nolo.com/legal-encyclopedia/illegal-eviction-procedures-new-hampshire.html))
....

New Hampshire's landlord-tenant laws do not apply to this situation.:


"540:1-a Definitions. – In this chapter:
...
IV. The term "tenant'' or "tenancy'' shall not include occupants or occupancy in the following places and the provisions of this chapter shall not apply to:
...
(d) A single-family home in which the occupant has no lease, which is the primary and usual residence of the owner.
..." Section 540:1-a Definitions. (http://www.gencourt.state.nh.us/rsa/html/LV/540/540-1-a.htm)

New Hampshire's landlord-tenant laws do not apply to this situation.:


..." Section 540:1-a Definitions. (http://www.gencourt.state.nh.us/rsa/html/LV/540/540-1-a.htm)[/INDENT]

Ah but the father is not the owner. The father is a leasee.

Also this part of the law:

I. A "shared facility'' means real property rented for residential purposes which has separate sleeping areas for each occupant and in which each occupant has access to and shares with the owner of the facility one or more significant portions of the facility in common, such as kitchen, dining area, bathroom, or bathing area, for which the occupant has no rented right of sole personal use.
http://www.lawserver.com/law/state/new-hampshire/nh-statutes/new_hampshire_revised_statutes_540-b_1

Would seem to convey that the OP is protected by illegal eviction laws.

Hopefully the OP will have access to a computer to return and let us know what happened.

Ah but the father is not the owner. The father is a leasee.
....

The father is the owner of the leasehold. The OP is the "occupant" as used in the definition I quoted.