Where to start....
First [in California], oral lease is ok for terms up to a year otherwise written agreement required. Perhaps this is what you meant.
The broad strokes: consider that, generally, folks are either tenants, lodgers or guests. How they are removed from private property varies according to each status. The gist of how you can tell follows.
A person is considered a
tenant only if they are
supposed to pay rent. This applies to your friends based on your description.
A
lodger is a person who lives in a room in a house where the owner lives. The owner can enter all areas occupied by the lodger and has overall control of the house -
most lodgers have the same rights as tenants.
However, in the case of a single lodger in a house where there are no other lodgers, the owner can evict the lodger without using formal eviction proceedings. The owner can give the lodger written notice that the lodger cannot continue to use the room.
How much notice? The amount must be the same as the number of days between rent payments. If paid weekly, then a week's notice and so on. In absence of a written agreement, it's then typically 30 days, the standard for most m-to-m arrangements.
So, when the owner [or, main/master original tenant having an agreement with the owner] has given the lodger proper notice and the time has expired, the lodger has no further right to remain and can be removed as a trespasser.
It could be argued that your friends are lodgers not tenants but I'm getting to that....
Now, a house guest is just that - a guest. Guests are not expected to pay rent. If the home owner tells a guest to move out and the guest refuses then the "guest" becomes a "trespasser". Trespass is almost always considered a crime and police are supposed to arrest criminal trespassers. No eviction is needed.
I'm not seeing where this strictly applies and that's a good thing.
Here's why you want to make sure the people you're kicking out
are actually houseguests and not t
enants. With or without a written lease someone who resides there full time and either pays rent as such, or
"helps" with utilities/expenses etc. or does specific assigned work around the house/grounds would likely be considered a tenant.
In many jurisdictions it is a criminal disorderly persons offense to perform a "self help" eviction without a court order.
Changing the locks, moving his stuff to the curb, turning off heat/hot water or other essentials can be considered constructive eviction and land the owner in a lot of hot water.
It would seem that the minimum amount of time/notice your friends are entitled to receive to vacate would correspond to the rental period in effect during the time they were still actually tendering rent payments and thereafter - 30 days.
The best thing for them is to make time tomorrow to find help staving off the immediate threat - not sure if they are even still there. I can't remember now what day you posted OP and I can't refer to it while I'm typing this reply.
PM me if you want and I'll try to get you at least one decent source near them that they contact asap for help adjudicating this kerfuffle that will, hopefully, not have to include the police and/or courts