The EU is not going to intervene in domestic sovereignty. The human rights violations would have to get extremely severe for that to happen, and I don't think there are explicit clauses in the treaties about it. That is a particular Rubicon they are not willing to cross.
I think the EU could theoretically kick them out, also there are some other kind of sanctions mentioned re Hungary which could be used but I don't remember which ones.
(or in this case, the checks map Oder)