OK, so what stops the TSA/DHS from saying "We suspect you are a terrorist; please unlock your phone"? Their actions have effectively said that for almost 20 years.
The same thing that stops all tyranny. A vigilant and engaged citizen body.
Practically, this means donating to the ACLU and related groups. It also means, if you’re party to injustice, suing or reaching out to organisation who can help you sue to assert our rights.
Because I'm interested, what would be the top three situations where that happened that come to your mind?
A tyranny must be recognized. See: https://en.wikipedia.org/wiki/American_Revolution
"The Continental Congress declared King George a tyrant who trampled the colonists' rights as Englishmen..."
If you recognize a tyranny but do nothing, you stand to receive further oppression. Consider the case of the PRC. The CCP is tyrannical toward those they rule; we plainly see this reality from our perch of liberty. However, unless the Chinese people recognize the tyrannical nature of the CCP, they'll continue receiving oppression. Making this realization harder is the PRC's surveillance apparatus and the population's indoctrination. I wish them luck.
And because they suppressed (non voting, poor) people in the UK didn't declare their king a tyrant it wasn't one for them.
I don't know the exact reasons people put up with tyranny. I suspect every situation is somewhat unique. However, answering that question would allow many future harms to be prevented.
The American revolutionaries declared King George III a tyrant, but that couldn't be the end; open rebellion would mean certain harm or death. So, they acted. They made a case for taking up arms against the crown. They then resolved to become independent (found in the Lee Resolution/"Resolution of Independence"). Two days later, they declared independence. And they fought. Note, though, that the Revolution required the recognition of tyranny.
IANAL, but my rough impression from the opinion is kinda. It seems like the reasonable suspicion can emerge entirely from the interaction itself, but that it should be based facts/reasons the agent(s) can articulate.
I found the section titled "7. Reasonable Suspicion, not Probable Cause, Applies to Both Such Searches" on pages 33-38 of the actual opinion (embedded on https://www.aclu.org/legal-document/alasaad-v-mcaleenan-opin...) provided good background on this.
The judge is evaluating one element of the relief the plaintiffs sought--that the agencies be required to expunge data copied during a search which, per the ruling, is unconstitutional. More specifically, the judge is addressing one stated reason for seeking that relief--concern that data obtained unconstitutionally will leave them forever flagged for extra scrutiny.
> "in the future, whether information has been retained from prior searches or not, agents must be able to point to specific and articulable facts for reasonable suspicion to believe that Plaintiffs’ electronic devices contain contraband, which also addresses the concern about any likelihood, greater than the general public of U.S. citizens returning to the U.S. borders, of being subject to a non-cursory search."
I agree donating to ACLU, EFF and similar orgs is our best option. Most of us do not get prosecuted unjustly, but we need to pool resources to defend those that do.
Like in a jury case, reasonable doubt doesn’t mean “a small level of doubt is acceptable”. It means that “aliens made me do it” is not sufficient to counter evidence.
The best approach is to know your rights, remind them of them, then let them do what they are going to do.
Bad searches get solved in court, not at the time of the search. You may get lucky and have them back down if it's clear you know they have no right to search, but I wouldn't bet on it.