The Dutch Civil Code is online
here (hope this link keeps working).
If you want, I can quote the relevant articles plus translation; they're quite easy.
I got curious about past changes in the law.
This recent article from a leading Dutch paper mentions a recent paper of Diane Paul and Hamish Spencer in an internet periodical "PLoS Biology", who argue there is no scientific basis for a ban on cousin-cousin marriages.
This article claims the current Dutch law has been introduced in 1970, in the first part of the complete reworking of the Dutch Civil Code. Before that, marriages were banned between relatives up to the 3rd degree - so parent/child, grandparent/grandchild or even great-grandparent/great-grandchild, siblings, and nephew/aunt or niece/uncle . But not cousin-cousin. There was the possibility for dispensation; a famous case was Anton Mussert, the leader of the Dutch Nazi party who married his aunt.
Finally,
this article claims that a ban on cousin-cousin marriages in the Netherlands had been lifted in 1580. It also mentions that the previous Dutch Health Minister had considered a ban on cousin-cousin marriages - the number is increasing among Turkish and Moroccan immigrants - but had not done so after advice from the medical world.
ETA: sorry all links are in Dutch. I can translate relevant parts if you're interested.