Well, it is when they are only going to be blocking donations coming from Finland.
The purpose of the Finnish law is "You can't get donations from Finns without a permit." Wikipedia doesn't have a permit, thus they can't get donations from the citizens of Finland.
Of course nevery charity in the world doesn't need to apply for a permit in Finland. First, the law doesn't regulate receiving donations. It's a restriction on soliciting the public for donations.
And second, Finland of course doesn't have jurisdiction over every charity in the world. But there is actually a Finnish non-profit branch of the WikiMedia foundation, who would fall under that jurisdiction. Their argument is that they have absolutely nothing to do with the fundraising, and it's all handled by the American WikiMedia Foundation.
The purpose of the Finnish law is "You can't get donations from Finns without a permit." Wikipedia doesn't have a permit, thus they can't get donations from the citizens of Finland.
Seems rather straightforward to me.