For a long time I was of a similar opinion to you that a closed start finish line should not be viewed as an obstruction. I have had a discussion regarding that situation with several different judges and the concensus that I got was that it is an obstruction, and must be treated as such, if it is deemed to be closed by the SI's.
I've long been of the opinion that a closed start/finish line is a bad idea. It exists only for the convenience of the race committee and does not serve the sailors. I sometimes call it "the lazy race committee rule". A closed line is also notoriously difficult to define properly in the sailing instructions. As a racer, I've never seen it written correctly. As PRO, I typically strike it from the SI's.
Ok, my personal opinion aside, if you are going to have a closed line, it's best if the sailing instructions explicitly declare it to be an obstruction as well. There's a good argument that it is implicitly an obstruction, and I would generally deem it so, but there's no guarantee that the protest committee will concur.
Regards,
Eric
US Sailing Certified Judge
Member, Area D Appeals Committee
