Most states require all kinds of hoops to evict a resident. Even without a a lease. You can’t just lock them out. Sometimes the penalties for a wrongful eviction can be severe. And, in some states, there are criminal penalties.

(As a practical matter, it rarely comes to this as a couch-surfer will go find another couch instead of wasting money on attorneys and the like. But, typically, the owner of the property can’t just unilaterally decide a resident is a trespasser and kick them out.)

Depends on the state. New York requires an ejectment hearing since he's family but in most states he doesn't have any more rights than a regular guest, since by his own admission he has never been asked to pay rent or contribute to expenses. Outside of certain cities with local protection laws, you can just change the locks when they leave.