Even if you are not fined you are still guilty of a criminal offence
The offence is failure to secure regular attendance at school of a registered pupil. That has been an offence since 1996. The fines have been around since 2003.
The only thing that has changed legally is that there is no longer anything in the regulations about allowing up to 10 days for holidays in term time in special circumstances. This was removed because parents, particularly with primary school children, were treating it as a right.
As has been repeatedly pointed out on these threads, every time a child is removed from school for a wedding or whatever it damages that child's education and disrupts the education of all the other pupils in the same class. Teachers mostly hate it when parents take their children out of school for anything other than sickness, although some choose to hide that fact in order to maintain good relationships with parents.
Weddings by their nature are exceptional
Not in the sense used in these regulations. It is perfectly possible to organise a wedding so that it does not involve children missing school. If you want children to attend that is the responsible thing to do.
The government should have produced proper guidelines about this and not left it up to Las and HTs
I strongly disagree. If the government produced a list it could not possibly take account of every set of circumstances with the result that absence would not be authorised in situations where any reasonable person could see that it should be. The head is best placed to make the decision as he or she is in possession of all the available facts about the circumstances. That is why the guidance from the government is limited to telling heads they should take into account, "the nature of the event for which leave is sought; the frequency of the request; whether the parent gave advance notice; and the pupil’s attainment, attendance and ability to catch up on missed schooling".