Groningen University (RUG) has a pretty good policy to improve the gender balance with full professors, which is generally embarassingly poor in the Netherlands.
However, the Committee for Equal Treatment received complaints from the Groningen student union that RUG has been discriminating men with the appointment of 12 full professors in 2010 and 2011. RUG created the posts especially for women assistant professors and men weren’t allowed to compete. This is against the law. The reason the student union filed the complaint is that, although they appreciate the efforts of RUG to improve the gender balance, more should be done about structural measures to improve the position of women professors instead, like making it easier to work part time.
The 12 women professors in question will not be required to relinquish their positions.
So technically, the reprimand was for discrimination, not for appointing women professors, but some reports in the media originally seemed to indicate that, hence this headline.