Green has complied with the definition of finish so I believe has finished.
I do not know what the SI was for, but parts of a finishing line do not have required sides, so I do not think Blue has finished but they may consider seeking redress.

Fully agree with Michael. Stupid SIs... or was the course shortened on the mark next to the RC boat ? If so, no way for a redress...

Michael,

Is it possible to see the SI which requires this? The specific wording probably matters a lot. Thanks.

Green has finished.  It doesn't matter what the Si's state because the SI's may not modify the definition of finish.

Not disputing that Green has finished. Let me rephrase: It will matter a lot to the competitors who don't drag around the detail of the definitions in their heads. The point is to see the primary document. So it can be used as an example of how not to draft SIs. Many of us keep collections of these.

Case 45   https://www.racingrulesofsailing.org/cases/668?page=5  suggests that in the case of request of redress Blue might receive redress, but this would be by the protest committee.   After discovering the major error in the SI's, the RC could request redress on behalf of the boat(s), but until that time Green is the only boat that finished..  

 Once had an RC in deep water for an upwind finish (shortened course), wind went from light to extremely light with a strong current which became the dominant factor for RC and mark drift.  The RC had a longer anchor line so it drifted to be behind the mark from the perspective of the competitors.  RC wisely did not move the boat as competitors were already heading towards the finish.  Competitors were moving with the current permitting a finish within the time limits.  They finished by crossing different sides of the line, sometimes choosing based upon their rights to other boats.  No one complained and it turned out our SI's had no language to make this a redress-able situation should a competitor request it.

I'm confused by Case 45 - it sounds like boat X received redress and got her finishing place (first) from the PC, but still appealed?

Definition of finish says "from the course side." Ordinarily this would be taken to mean "from the direction of the last mark", but wouldn't a requirement to leave the RC boat finishing mark to port make the left side of the line in Catalan's diagram the "course side"? If so then the SI would not have changed the definition of finish and would be valid, so Blue would have finished and Green not.

Dan,

I think that case 82 https://www.racingrulesofsailing.org/cases/807?page=9 deals with the incident you covered.

Thank you Peter, will pass that along to our club.  It's laughed about at the bar every so often which indicates to me that there is lingering interest in the validity of the race.

According to the definition finish and the diagram, Green has finished because she “…crosses the finishing line from the course side.” (i.e. sailing from the previous mark of the course). Blue did not, so she has not finished. To state in the SI “…that boats must leave RC’s boat port tacked” (I guess in order to finish) is a change to a rule (see rule 85.1) which is not permitted by rule 86.1(b). A request for redress by Blue, in my opinion, wouldn’t pass the test of “through no fault of her own”.  

This situation can happen often when weekly races are held where courses are set on the water around permanent marks.   An RC might set the course for 2-3 laps.  In such SI's, it is common for the finish-pin to be the last mark indicated on the course board (we had this nearly every week in the Magothy River north of Annapolis)

For instance, consider the following course set by the RC by boards (not to scale obviously) .. B-red, C-red, A-green, 2x. 

An RC might flip to the other side of the pin for the finish, but she need not do so because the definition of finish will override A's starboard designation at the finish automatically. The RC can keep her options open to shorten some classes and continue others.

Peter is correct Dan, the appeal goes back to the 80s, I remember it well! 

Assuming 
1.  wind is coming from top of page and
2.  PC is run of the the mill club sailors (or worse: the authors of that SI)
Smart course is Green’s (clearing the line) followed by a tack and re-crossing on port tack.
[cynical face]

I would need to see the SI for this.  What can "leave the RC's boat port tacked" possibly mean!   It  does not say "finish" or cross the finish line port tacked.  Green has finished in the usual sense.  (I would expect green to gybe or tack  to bring her onto port tack after finishing and leave the area of the committee boat.  Such an SI might be a poorly worded attempt to keep competitors from wandering into a restricted area, like another racing circle)  As for Blue-without the specific language of the SI, it is pure speculation how Blue ends up.  

Our RC generally ascribes to the theory that competitors should cross the line as presented, perpendicular to the last leg, as stated in our SIs,  as sometimes RC boats and finish marks have to be moved, somewhat unpredictably.  In once case, the RC boat anchor was hung down, and with no support boat to move the start mark, presenting boats coming downwind with the RC boat to port and the finish boat to starboard.  The SIs said all marks to be left to port-but also stated that the finish line should be crossed as presented.    Some boats left the start mark to port, tacked around it it and then crossed, others went straight for and crossed the line.  The boats that left the finish mark to port were scored DNF, and redress denied based on the SI, which they were unaware of, having failed to read them beforehand.  Boats that finished properly and opposed redress all referred to the rule in the redress hearing.

Stephen,

I suspect that the 'Original Poster' was meaning an SI which said...

"Race Committee vessel should be left to port side."

If so, then the supplied diagram presents a common scenario which has been asked and answered many times, but clearly still causes problems.

Most has been covered already in this thread (though surprised Case 129 not yet mentioned).  The rules are clear.

The hook finish situation is covered in Case 129 and the question of the improper SI is covered in Case 45.  No need to repeat these.

I believe the original case came from the RYA Casebook 1980/2.