My reading of it is that it is a wry jab at the 'sort of people who make laws about lighting bicycle lamps'. The narrator judges them to be bossy sort of people who like their word to be law. Hence if the sun did not set at its appointed time they would demand that the sun provide them with an adequate explanation of his aberrant behaviour.
The rules surrounding lighting bicycle lamps at that time were to be found in the Local Government Act of 1888 and state:
bicycles, tricycles, velocipedes, and other similar machines are hereby declared to be carriages within the meaning of the Highway Acts ; and the following additional regulations shall be observed by- any person or persons riding or being upon such carriage :-
(a.) During the period between one hour after sunset and one
hour before sunrise, every person, riding or being upon such
carriage shall carry attached to the carriage a lamp, which
shall be so constructed and placed as to exhibit a light in the
direction in which he is proceeding, and so lighted and kept lighted, as to afford adequate means of signalling the approach
or position of the carriage ;
It is interesting to note that while current laws require the use of lights 'between sunset and sunrise' the older rules allowed for riding un-illuminated in the twilight for an hour at each end of the day.