I found Keith's answer excellent (+1) and agree completely with it.
What is left is to apply it to the given question.
Now, I feel (as a non-native speaker) that it is possible to use "this" to refer to any time. However, the context should be such that the word feels as (quoting Keith):
"this" is something central and implicit in the statement
The "move" is finished when the player releases the piece. At this time the button on the clock should be pressed.
Here the present simple is used to express a rule (as it is used to express habits and routines) - actual time is only grammatically in present, the rule applies to future and past. If we put it into past tense
The "move" was finished when the player released the piece. At this time the button on the clock was pressed, but the clock was broken and the match was stopped.
This does not sound to awkward to me, although that can substitute this with no loss in meaning.
Overall, if you can keep "this" central to the statement so that it can be easily and implicitly understood to which time it refers, I feel as if it can be used.
In the example you are asking if in:
It is important to note, however, that jurisdiction at this time did not include legislation, which virtually did not exist until well into the 15th century.
the use is improper.
However, here, I would say that it is permissible; it is often the case that in history text the narrator transposes the point of view so that here, this, now and so on refer not to the readers present, but to the present of the events and vicinity of places that the text talks about. Keith's criterion still applies - such use of "this" is implicitly obvious. It works quite well if the events (or places) are presented chronologically.