early disembarkation before cruise ends

[PrincessShmoo]

I think it is a long shot. As someone said above it has to do with a non US ship can't transport passengers between two US ports. I think it is called the Jones Act.

Actually, no. The Jones Act applies to cargo. What (might) apply would be the Passenger Vessel Services Act, which applies to passengers. The PVSA prohibits a foreign flagged ship from transporting passengers from one US port to a different US port without stopping in a distant foreign port. As this cruise is a round trip cruise from a foreign port it doesn't fall under the PVSA rules.

That said, most cruise ships generally don't permit disembarking from a different port than the one the passengers are supposed to disembark at (the final port). It does happen, however, you just have to make arrangements BEFORE the cruise with the cruise line as to the procedure they will allow.

We saw one of the entertainment acts disembarking in Juneau to fly home so it must be legal.

Entertainers do not fall under the purview of the PVSA, as they are not paying passengers.