Unpublished changes to travel rules

However in this case, the foreign country hasn't published the rules, so there were no way the travelers or the airline could have possibly known about these changed rules.

This statement that Austria didn't publish the new rules beforehand is simply not true.

It was published in different news sources on the 23rd of December, but it seems, not widely in the British press.

Unfortunately, the Wayback Machines seem to have started their holidays after the 22nd of December since that is the last date that one can retrieve anything from the relevant government sites:

• Wayback Machine: Entry into Austria and pre-travel clearance

The BBC report (2021-12-28: BBC News - Austria's Innsbruck airport denies 110 Britons entry over new Covid rules) was published over 24 hours after similar reports in the Austrian, German and Italian media.

So this looks more like a holiday season reporting problem.

Would these passengers have any standing to recover any costs? Obviously not from the airline, but what about the destination country in some way? What about travel insurance?

Since there is at least one British news report (see below), quoting the new Austrian regulations, 2 days before they came into effect this is unlikely for both cases.

The only British news source that I can find from the 23rd of December is:

Austria travel restrictions and latest advice | The Independent.
Helen Coffey, Lucy Thackray 5 days ago [as of 2021-12-28]

Austria has once again tightened its rules for UK travellers, after adding the country to its “virus variant list” (virusvariantgebiete) of high risk destinations.

The rule change comes in from Christmas Day and will affect many British winter holidays, especially in the ski sector.
...
Can Britons travel to Austria?.
Yes, but only some will avoid lengthy quarantine.

As of 25 December, the UK is being added to Austria’s ‘virus variant list’, a list of high-risk destinations for the omicron variant.

This means that only travellers with a proof of two vaccine doses and a booster jab, along with a negative PCR test result, will be able to avoid quarantine in the country - everyone else must quarantine for 10 days.

The test (PCR, LAMP or TMA) must be taken within the 48 hours before your time of arrival.

The new rule comes in from Christmas Day and will mean many cancelled holidays for families whose younger members have not yet received a booster - some may not even have received two jabs.

The Austrian and German press also reported the changes extensively on Thursday the 23rd:

Österreichs Einreisebestimmungen - news.wko.at.
23.12.2021, 16:35.
Übersicht Einreiseverordnung NEU per 25. Dezember 2021.
...
NEU per 25.12.2021.
Die Staaten Vereinigtes Königreich, Niederlande, Dänemark und Norwegen wurden in die Liste der Virusvariantengebiete (Anlage 1) aufgenommen. Die Einreise aus Virusvariantengebieten und -staaten (Anlage 1) ist grundsätzlich verboten. Dieses Verbot gilt z.B. nicht für EU/EWR-Bürger. Deren Einreise ist nur mit einem negativen PCR-Test zulässig. Es besteht jedoch grundsätzlich eine Quarantäne- und Registrierungspflicht. NEU ist, dass für alle Personen, die einen Nachweis einer „Booster“-Impfung sowie einen negativen PCR-Test (ACHTUNG: in diesem Fall darf der negative PCR-Test nicht älter als 48 Stunden sein) mitführen, die Quarantänepflicht entfällt. Die neue Verordnung gilt vorerst bis 31. Jänner 2022.

Overview of entry regulations NEW as of December 25, 2021.
...
NEW as of December 25th, 2021.
The United Kingdom, the Netherlands, Denmark and Norway have been added to the list of virus variant areas (Appendix 1). Entry from virus variant areas and states (Appendix 1) is generally prohibited. This prohibition does not apply to EU / EEA citizens, for example. Their entry is only permitted with a negative PCR test. However, there is basically a quarantine and registration requirement. NEW is that for all persons who have proof of a “booster” vaccination as well as a negative PCR test (ATTENTION: in this case the negative PCR test must not be older than 48 hours), the quarantine obligation does not apply. The new regulation is initially valid until January 31, 2022.

Österreich schickt Urlauber direkt nach Landung zurück - Österreich-News | heute.at.
27.12.2021, 14:50 Uhr.
Falsch oder gar nicht informiert.
13 Flugzeuge waren am Sonntag [2021-12-26] in Innsbruck aus dem Vereinigten Königreich kommend gelandet. Für 110 britische Passagiere war jedoch mit dem Flug die Reise schon wieder vorbei. In der Ankunftshalle des Flughafens konnten sie nämlich keine Booster-Impfung samt negativem PCR-Test vorweisen. Rund 70 der Touristen wurden direkt wieder in einen Flieger nach Großbritannien gesetzt, bei 40 Personen war der Heimflug nicht mehr möglich.

"Diese wurden ebenfalls an der Grenze abgewiesen und über Anordnung des Landes Tirol vorübergehend in einem Hotel untergebracht", heißt es von der Landespolizeidirektion Tirol. Am Montag begannen die Abklärungen mit dem Stadtmagistrat Innsbruck als zuständige Gesundheitsbehörde, die Betroffenen hätten sich "sehr diszipliniert, höflich und verständnisvoll" verhalten. Sie alle gaben an, falschen Informationen im Internet zu den Einreisebestimmungen aufgesessen zu sein.

Austria sends holidaymakers back directly after landing - Austria News | heute.at
Incorrectly informed or not informed at all.
13 planes landed in Innsbruck from the United Kingdom on Sunday [2021-12-26]. For 110 British passengers, however, the trip was already over with the flight. In the arrival hall of the airport they could not show a Booster vaccination or a negative PCR test. Around 70 of the tourists were put directly on a plane to Great Britain, 40 people were no longer able to fly home.

"These were also turned away at the border and temporarily housed in a hotel by order of the state of Tyrol," said the state police department of Tyrol. On Monday, the inquiries began with the Innsbruck city council as the responsible health authority, saying that those affected had behaved "very disciplined, polite and understanding". They all stated that they had eaten up wrong information about the entry requirements on the Internet.

There is already a very good answer, but here are some supplemental thoughts.

The obvious question which astonishingly none of the articles dive into is "what happened to the other flights from the UK to Austria that day?". As far as I was able research this, there were no similar occurrences and it seemed to be mostly an isolated incidence. That also means that the information WAS available to the majority of airlines and passengers that day and that the whole discussion about which website was updated when in which language is just political posturing. Unfortunately, this another example of irresponsible press coverage: instead of doing a little bit of research to get to the bottom of what actually happened, there is just random speculation. It's sad to see that from the BBC.

This in turn begs the question. "What was different about this flight?".

The answer in this case is probably "easyJet". Most governments rely on the airlines to communicate and enforce rules to their passengers. Legally, it's the passenger's responsibility, but this has become so cumbersome and error prone that it's in the best interest of the airline to help out. It's possible that easyJet has simply given up doing that: I flew 3 months ago from AMS to BER and they carefully checked my documentation. I did the same flight two weeks ago and they checked absolutely nothing (even though the Netherlands were classified as a "high risk area" by Germany at the time).

Would these passengers have any standing to recover any costs?

No. Proper documentation is always the passenger's responsibility.

what about the destination country in some way?

No. Apparently the information was available to most airlines and passengers so the government not at fault here. Even if they were: getting money from a government is a losing battle.

What about travel insurance?

Depends on what the policy covers. It's very unlikely though, since the passenger made the mistake here.

From a legal perspective, in most jurisdictions there is no requirement that the law be "published" in the form of guidance, media announcements etc. This derives from the well known principle that "ignorance of the law is no excuse".

In the UK for example, all Covid-related rules are given effect by way of primary or secondary legislation. They become law the minute the bill is given royal assent and becomes an Act (primary legislation) or when they are made according to the applicable procedure (secondary legislation). It is up to you to make sure you are familiar with every Act and Statutory Instrument which is passed (however impractical that may be in reality) and the law assumes that you have done so.

Accordingly, you are unlikely to have any recourse against the government.

Government guidance rarely has any intrinsic legal effect and there is usually no requirement that it be written or published. Some exceptions exist; in such cases the enforceability and/or requirement to publish will be stated in the applicable legislation. In those cases you might have some recourse, but that would depend on the specific law and facts.

Whether or not you could claim against your travel insurance is a contractual matter - you'd have to check your policy terms. I've personally never seen a clause which protects you from ignorance of rules.

1. Confer Who pays return ticket if denied entry?
2. There’s generally no actionable right to enter a country. I wouldn’t even be so sure you couldn’t be denied from entering the country you hold a (sole) citizenship of. As far as I understand the mentioned CoViD?19 rules apply indiscriminately of nationality.
3. Mid-air changes of regulations aren’t forbidden. In the movie The Terminal for instance the destination country stops recognizing a passenger’s nation thus barring him from entry.
4. National laws of Austria must be published in the Federal Gazette first before they can possibly take effect (the next day soonest). Administrative Acts must also be announced in a dedicated paper, but here you also have the option to announce them individually to appropriate addressees, so they can actually become effective immediately.
5. Generally, in a state governed by rule of law people have the right to presume the state acts in a predictable manner according to its laws. However, suing the state for compensation is only feasible if there was a positive statement you could expect a certain behavior from the state. In this particular case though you have no credible interest, especially since State Departments around the globe have posted general CoViD?19 travel advisories mentioning the circumstance of swiftly changing regulations.