The Constitution clearly incorporates so-called "exceptions" to the warrant requirement. The Fourth Amendment to the Constitution prohibits unreasonable searches and seizures but does not condition the reasonableness of any search/seizure on the existence of a valid warrant. Rather, a warrant is essentially a safe-harbor that makes a search/seizure presumptively reasonable.
The question then becomes whether a "no refusal" checkpoint search, without a warrant, is reasonable under the particular facts and circumstances. Allied to that question is whether a "no refusal" checkpoint search infringes on an individual's reasonable expectation of privacy (one of the touchstones of reasonableness for warrantless searches/seizures).
In the case of an individual operating a motor vehicle the answer is not at all clear-cut. To start with, a drivers license - and hence the ability to legally operate a motor vehicle on public roads - is a privilege, not a right, which means that the State in which an individual drives may condition that privilege in ways that the exercise of a right could not be conditioned. Requiring drivers to submit to a "no refusal" checkpoint for the purpose of ensuring that all drivers are not, at the time of the check, a danger to the public and themselves due to intoxication/inebriation.
With respect to a reasonable expectation of privacy, if a State has well-publicized the existence of, and its intent to use, "no refusal" checkpoints, then it's unlikely that a driver would have a reasonable expectation of privacy that he or she not be subjected to the search that such a checkpoint entails for the simple reason that he knows, or should know, that the checkpoints are being used and therefore cannot reasonably expect to be exempt from such a checkpoint.
The bottom line is this: "no refusal" checkpoints are no doubt offensive and intrusive, but they are most likely constitutional and the only remedy is political: for the people of Oregon to persuade their elected officials to not use such checkpoints.
Failing that, the only real alternative to not being searched at all is to simply not drive in Oregon. That in and of itself might add some persuasive weight to the demand that elected officials stop using such checkpoints if the number of people who choose to not drive in Oregon causes significant economic pain to the state.
It is not merely our Constitutional right against unreasonable searches and seizures at stake here. The right against self-incrimination also applies, and it is s slippery slope indeed when a state government may legally employ an arbitrary standard (blood alcohol level) to determine who is "inebriated" and thus presumably a public danger while driving.
I understand your argument about public safety exceptions to the 4th Amendment, but I believe that practices such as Oregon's stretch that exception beyond the breaking point.
If the police power were employed to test all
drivers at a given highway checkpoint, and notice of such testing were provided in advance to all who might be so affected, one might make the argument that the use of BAL testing in that instance would be neither arbitrary nor capricious, and that no reasonable expectation of privacy existed for the class of drivers so informed in advance.
But the fact is that not
all drivers are subject to testing, and the decision on who to detain and test is not
based upon police observation of behavior (e.g. - swerving, open containers, bloodshot eyes) leading to reasonable suspicion. Further, the use of an arbitrary blood level standard (0.08%) is problematic, in that such a standard does not in and of itself prove impairment, and in fact has been scientifically demonstrated to be insufficient to actually result
in impairment for many (although not all) adults.
Many people can achieve a BAL of 0.08% after having drunk just a single pint of beer or a large glass of wine. Many of the same people will not demonstrate any visible impairment in driving performance or judgment. A few, will. Under previous standards, police needed to observe evidence of such impairment and then make a determination based upon their observations and physical testing (e.g. -the ability to walk a straight line) as to whether a person was or was not intoxicated. Now, all they need is a number on a meter; such a standard creates the illusion of scientific analysis by employing a convenient, uniform standard that disregards human physiological reality.
Lost in all of this, along with the critical presumption of innocence, is common sense. And that is no accident. Because as with so much else today, the primary purpose of government is no longer held to be the protection of rights (including the right of people to be safe on the highways), but rather to impose control over all.