While I understand that the Sheriff feels he's between a rock and a hard place, I take issue with this part:
OSSA was not consulted when this measure was crafted and completely understands the uncertainty caused by this measure, however the measure was passed by a majority of Oregonians. Until such time as all or part of the measure is stayed or found unconstitutional by a court, the measure is the law in Oregon.
That's a cop out. The majority of people should not get to abridge the rights of people, even for as long as it takes the courts to play out. If something is blatantly unconstitutional, it should not be enforced, and people trying to enforce it should be stopped. Since this measure effectively stopped the 2A in Oregon, we can skip all the mealy mouthed "It's not an infringement yet" arguments. On Dec 9th you can't buy a firearm in Oregon.
What the Sheriff's Association should have said, is "This is a blatant blockage of an enumerated right, and we will not enforce any part of it until, at minimum, a court trims it down and affirms constitutionality. Furthermore, any person, local state or federal LEO that attempts to arrest or detain someone based on this law until it is affirmed as constitutional, will be arrested for false imprisonment and held until the legal process plays out."
You don't ship the people to Siberia first, and then see how the appeals play out.