If you mean to imply I haven't researched the law, you're correct. I'd be glad to be educated. But from what I understand, it's a complex area of law and this particular issue is not yet settled, and won't be until the S. Ct. has addressed it. (And anyway, i.m.h.o., the S. Ct. and other conservatively-oriented courts have been taking a lot of wrong turns on Constitutional interpretation lately.)
Glad you mentioned sobriety checkpoints; I was wondering about that but wasn't sure what phrase to google. Wikipedia says:
Legality in the United States
The Fourth Amendment to the United States Constitution states that: “The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.” At a sobriety checkpoint, drivers are necessarily stopped without reasonable suspicion, and may be tested summarily and without probable cause. Thus the Constitution would appear to prohibit people from being stopped without a search warrant or at least without probable cause that they have committed a crime; however, the warrant requirement only attaches should the search be unreasonable and the Supreme Court, as shown below, decided that such stops are not unreasonable under certain circumstances.
Driving under the Influence of alcohol is a special type of crime, as driving with a blood alcohol content (BAC) over a set limit is defined as the crime; it is not necessary to drive recklessly or cause an accident in order to be convicted. To determine BAC accurately, it is generally necessary for the driver to subject themselves to tests that are self incriminating, and drivers sometimes exercise their right against self incrimination to refuse these tests. To discourage this, some jurisdictions set the legal penalties for refusing a BAC test to equal or worse than those for a failing a BAC test. In other jurisdictions, the legal system may consider refusing the roadside alcohol breath test to be probable cause, allowing police to arrest the driver and conduct an involuntary BAC test. The Michigan Supreme Court had found sobriety roadblocks to be a violation of the Fourth Amendment. However, by a 6-3 decision in Michigan Dept. of State Police v. Sitz (1990), the United States Supreme Court found properly conducted sobriety checkpoints to be constitutional. While acknowledging that such checkpoints infringed on a constitutional right, Chief Justice Rehnquist argued the state interest in reducing drunk driving outweighed this minor infringement.
Dissenting justices argued that the Constitution doesn’t provide exceptions. "That stopping every car might make it easier to prevent drunken driving...is an insufficient justification for abandoning the requirement of individualized suspicion", dissenting Justice Brennan insisted.
Chief Justice Rehnquist argued that an exception was justified because sobriety roadblocks were effective and necessary. On the other hand, dissenting Justice Stevens countered that "the findings of the trial court, based on an extensive record and affirmed by the Michigan Court of Appeals, indicate that the net effect of sobriety checkpoints on traffic safety is infinitesimal and possibly negative."
Jurisdictions that allow sobriety checkpoints often carve out specific exceptions to their normal civil protections, in order to allow sobriety checkpoints. Although the U.S. Supreme Court has found sobriety checkpoints to be constitutionally permissible, ten states (Idaho, Iowa, Michigan, Minnesota, Oregon, Rhode Island, Texas, Washington, Wisconsin, and Wyoming) have found that sobriety roadblocks violate their own state constitutions or have outlawed them. Two other states (Alaska and Montana) do not use checkpoints even though they have not made them illegal. <12>
It seems to me that the TSA scans and gropings are far more invasive.