How so? The practice of marriage is a positive or at least value neutral practice. Are you suggesting that permission of the practice of positive or value neutral acts endorses harmful acts? I'm just not following your logic here.
In my opinion.
For the purposes of this discussion, I will ask you to agree to define marriages as legally acknowledged promises of mutual support and responsibility. It is not very accurate a definition, but hopefully it will be useful enough for now.
Despite common misunderstandings, those marriages are the responsibility of the state, not of any churches. They must be ultimately approved by the state if they are to have legal worth. And legal worth is necessary for things such as effects on taxes, custodianship of progeny, inheritance rights and the like. Apparently marriages in Norway must be informed to the Tax Authority, among other requisites.
It is very true that many churches choose to officiate marriage rites of their own, often by way of priests who have authorization to perform both forms of marriage at the same time in a single ceremony. It is not entirely clear to me whether that was ever the case for JW priests in Norway, but I assume that the newspiece is talking about marriages with legal weight, for the very simple reason that governments have no means and no authority to make decisions about purely religious marriages.
At the very least, I have to assume that any previously existing agreements of official recognition of the religious authority of JW priests to officiate marriages that rely on the acknowledgement of the JW as a church will lose validity. In effect, the JWs are losing a license due to not fulfilling the necessary requisites.
There is also another, slightly less obvious reason to revoke any legal license of JW priests to perform marriages. A license would give at least the appearance of the authority to decide whether any given couple fulfills the requisites to marry. Without some form of accounting to government, it would be tricky or worse to avoid abuse of that authority. What if a priest tells the couple that he will not marry them? They can reach for other marriage officer, perhaps from outside the church, of course. But that amounts to creating quite unnecessary estrangement and controversy.
Whether JW's in Norway want to perform their own marriages regardless of official recognition is entirely their decision, of course. They just won't have legal value.
Religious and lifestance-based organisations
Getting married | Norge.no