TL;DR: This particular grocery question isn't helpful because there is no good evidence anyone believes the claim. This reveals a problem with the rule we have been following; we should fix the rule.
The General Case
I think the Photo Id for groceries question is a clear exception to the original rule, and therefore I would like to see the original rule updated.
Here is the original rule from the question: What is a 'notable' claim?
The main way of demonstrating notability is showing the claim being mentioned in the media. Examples include: books, newspapers, mainstream television, or widely-known web-sites including major blogs and Wikipedia. Claims put forward by a celebrity are also automatically considered notable. The idea here is that once a large number of people are exposed to the claim, it is of general interest to validate the claim and either confirm or refute it.
To be clear, this is a situation where I did break the rule, openly, but I think that it was warranted, because the rule lead to a situation that contradicted its intention.
There are several reasons for requiring notability.
One reason is to ensure that the original claimant actual made the claim (and not as a joke, fiction or simply misspeaking).
Another is to ensure that many people believe the claim - enough to warrant spending the effort to investigate it properly. (I think this might be one area where people disagree about what should be in scope, because they have different understandings of how long it takes to edit a good question, and how long it takes to write and edit a good answer. I don't want >1 hr to be wasted by others on answering rubbish questions.)
We have accepted a celebrity saying a statement as a short-cut for showing many people believe it. However, in situations like this one, the short-cut is inappropriate. We need to have an exception clause for the rule.
I am open to suggestions on how that is worded.
The Specific Case
Several commenters have disagreed with my assessment on this particular Grocery Id question.
Let me start with: Sorry, but we don't care about your political opinions I am not here to support Trump and I am not here to attack Trump. Where politicians express opinions or morality, this site should keep clear. Where politicians demonstrate some aspect of their personality that some people like or don't like, this site should keep clear.
Sure, where politicians express factual statements about the world that people believe, that might be on-topic.
Sure, the OP might not be confident a politician's claim is false, and be looking for quality evidence to support that belief.
But, if it is straight political "gotcha" questions where the OP knows perfectly well that it is false, and just wants to share a laugh at a mistake by a politician on the other team, I don't think we need it here. Take it to Twitter.
Arguing that everything from President Trump, in particular, is on-topic because he makes so many misstatements is an ad hominem attack, and I don't think it warrants a special policy.
In this question, it is blatantly obvious to everyone - Trump supporter or no - that the literal claim that you are required to produce id to buy groceries in the USA is false.
We aren't "making the Internet a better place" by debunking the claim here.
For most people in the USA, it is clearly false from personal experience. But, we don't accept that argument here (although one deleted answer tried to). The level of rigor required for definitive answers on Skeptics.SE is very expensive for such an easily dismissed claim.
Several people have tried generously interpreting the claim to make it somewhat true - oh, he was referring to alcohol, he was referring to cigarettes, he was referring to using some forms of credit cards, membership cards, SNAP etc. That's a fun game to play, but this isn't the site to play it.
Some people have tried understanding what Trump's beliefs are - does he really think that id is always required? Did he misspeak? None of that is on-topic here.
Some people have argued that other sites have debunked it, therefore it is notable. I think that is wrong on three grounds:
This doesn't show anyone believes it. It shows people don't believe it. (If an OP, in good faith, believed a debunking was wrong, it would make a great question, but that isn't the case here.)
Other sites may be politically motivated - shooting down Trump's statements may make them more popular amongst readers that are Trump detractors, even if none of them believe the statement in the first place.
If anything, it is an argument that we don't need to solve this one, because anyone searching finding our site would also find these others. We aren't making the Internet a better place.