Wrong severability analysis, again --and-- why would you use an unconstitutional guideline as advisory?

I have been informed that Judge García-Gregory has held that Blakely applies to the sentencing guidelines and has held them unconstitutional in their entirety, but will use them as, well, "advisory." This is all hearsay information, but Rachel promised a real run-down on each Judge's stance and I'm still waiting for her report to be posted.

Now, why would a Judge use the guidelines as "advisory" if he finds them unconstitutional? What exactly does a Judge mean when he says he will consider the guidelines as advisory? And I have a further question: Why is the severability analysis being done solely on the sentencing guidelines, rather than on the statute (the Sentencing Reform Act)? If we view the guidelines as agency regulations, the ususal thing that happens when the Courts examine a regulation and find it unconstitutional is that they simply discard it, period. The agency will come up with a new regulation that will comply, or none at all. And if the Courts do any severability analysis it is not within the regulations themselves, but in the statute, here the SRA. So why are all these courts not doing this? Am I missing something here?