there was a lot of talk about this a few weeks ago on the Yahoo groups when the first potential shutdown was imminent. Apparently when it happened back in 96 or whenever it was no one was allowed to launch and all accesses were locked/chained, inaccessible. Essentially, if your launch is then you are screwed.
check the GCPBA and rafting_grand_canyon groups, can't remember where I saw it. I think someone even mentioned that last time they had security or local law enforcement there to make sure no one could access the park.
I know it's our park, don't shoot the messenger. just what I read.