> Unfortunately, it's only advisory.
True, but in additition to this advice, there is the Department of Foreign Affairs official travel advisory (the kind that every country issues, like "due to a civil war, we advice against all non-essential travel to country X") [1]. That advice is currently to avoid all non-essential travel to all countries, except the whitelist that is updated every two weeks. As of right now, that whitelist consists of the countries or subnational regions labeled as green on this map [2]. This is not just splitting hairs on my part: by violating the latter type of travel advisory, your health insurance is likely void, you are to expect no assistance, and you are subject to a mandatory quarantine on return, for which there is no paid sick leave.
> The government should set up a 5000 NOK (at least) "traveling fine" per person, and obligatory quarantine
For all the non-exempt countries, i.e. for most of the world, there is obligatory quarantine on your own dime. Unless your job allows you to work from home, that's a substantially larger financial penalty than the fine you suggest.
> ("home" confinement in state-provided guarded quarters)
Oh come on, this isn't China.
> The national health institute here opines that closing the borders has questionable or no effect, even though most of the cases in the 1st wave got imported from ski-resorts in Italy.
You seem to be aware of the whitelist of countries (even though you misrepresent the situation at the beginning of your comment). Then you are probably also aware that the idea is that the whitelisted countries have a low enough case rate that the authorities believe that closing the border to those countries has little effect. This may or may not be correct, but you seem to try to view the situation as negatively as you can.
[1] https://www.regjeringen.no/en/topics/foreign-affairs/reisein...
[2] https://www.fhi.no/nettpub/coronavirus/fakta/reiserad-knytte...