From where cometh that /obligation/necessity?

Is itsubjective or objective deontic obligation/necessity that is being expressed here?

Most Americans view the federal government positively, but there still are some enduring stereotypes that must be dispelled, according to a study released Wednesday by the Partnership for Public Service.

Photos and articles in young women's magazines help convince many teen girls that they are fat and must diet, according to a study published in "Pediatrics."

As inmate population ages, prison system must adapt, according to a study conducted by researchers at the San Francisco VA Medical Center and published in ...

Quebec journalists argue that their responsibilities differ from those of English-speaking journalists because they serve readers and audiences that have different needs. As the virtues of confederation are not taken for granted in Quebec, all political options, including sovereignty, must be discussed and evaluated. According to Susan Delacourt,

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CalifJim wrote:

The according to seems to have struck you as important, I surmise.  Does that mean these are all subjective by your definition of subjective? CJ

Yes, I'd say they are all reporting personal judgements on necessity, but I may be wrong, as I'm told that AE speakers do not distinguish between uses of deontic must and deontic have to.

<I made the observation that deontic must sounds more "official" to Americans.  Maybe that's the according to connection, i.e., according to suggests an authority, an "official".   I don't know how to relate my idea of "official" to your idea of "subjective".  >

Most of us would relate the "according to" with "on the authority of". But, is it still an only opinion towards the proposition of the sentence? If so, I'd say that it's subjective modality.

And isn't according to modal in a sense? It seems to say "this is not necessarily true for me, the speaker", "I'm just telling you the case in another world".

<Have a lot of other Americans had the same reaction?>

Yes.

Interesting. I can only find one Google example with the words "must" + "according to a law passed..."

"A different obstacle appears on the Israeli side, where any territorial concessions must be ratified, according to a law passed in the waning days of the Netanyahu government (and recently toughened), by a referendum. "

And one with "have to":

Soccer hooligans travelling to this summer's European Championships in Belgium and the Netherlands will have to watch it, according to a law passed by the Upper House (Bundesrat). Now hooligans who were banned from leaving Germany, would commit an offence if they did.

One with "should":

When a minor seeks an abortion, the other parent of the child to be aborted should be notified, according to a new law passed in February by the Washington State Senate. The law still needs to be approved by the House and the Governor.

<... must go ...:  Not said this way in AmE.   Can't relate to it.  We'd substitute ... should go ...  To me this sounds like a case of British exaggeration.  The core intended meaning is the should of advisability, not the must of obligation.  (It is highly/really advisable that John go to the doctor's.  Not: It is highly/really mandatory that John go to the doctor's.)  I think that the British speaker tends to overstate these, using must where should is sufficient and actually more accurate.  The word really is the give-away.  must in its core meaning would not require really since it's already absolute.  (Note the weirdness of the paraphrase highly/really mandatory above.)>

So in the case where a guy has cut his hand and is bleeding profusely, an AE speaker would say "you should go to the hospital", right?

And these would be impossible in AE, right?

You must come and see what I bought for Jan's birthday.

You must see the new Stallone film. It's great.