Can questions be closed for a reason that is valid TODAY but did not exist at the time the question was asked?
Here is an example.
Why close a 2 year old question?
Questions are now "routinely" closed for "polling." Depending on the site, people came to a "consensus" about this some time in the past two years. But the question was asked two years ago. And suppose this was before this consensus was formed? Are there ways of "grandfathering" such questions?
Short answer, "yes". There are ex-post-facto closes.
Longer answer....
There has been an uptick in close activity over the past ... 6 months or so. My interpretation of this is that the community is coming together to more clearly define what is on-topic and constructive for the site versus what is not. In many ways, this is continued evolution of the site; especially in light of the scope change enacted effectively eons ago. That conversation has been hashed to death many times already and I'll leave it as an exercise to you to dig through meta for the relevant questions & answers. The general point is to clean up the lesser quality stuff that provides bad precedent for new, bad questions.
Poll questions and resource questions (aka book requests) fare very poorly now, which is a good thing, IMO. A while back, many of those had been closed as off-topic but the current trend is to close them as not constructive.
Others in that vein are being closed as duplicates. And as Bart van Ingen Schenau noted, an older question may be closed as a duplicate of a newer question. It introduces an anachronism, but the newer question may represent a better "answer" for that particular theme. Or it simply could have been the question that the close voters found first. Don't read too far into that aspect.
RE: historical locks - if a question is particularly noteworthy and well up-voted, then it may be a candidate for a historical lock. This helps keep it from deletion as it potentially has useful information for future visitors.
RE: grandfathering old questions - not a chance, honestly. The problem is that "newer user" will site "really old question that's now blatantly off-topic" as the basis for asking their blatantly off-topic question. The community tries to explain "it's not like that anymore." Feelings are hurt; pedantic rage-quits occur; most folk involved still standing are left feeling vaguely annoyed. Closing off those old questions cuts down on the likelihood of the above annoyance. With some 25k+ questions on the site now, there's really no other way besides closure to indicate the change in the site direction.
