I heard of a case where the paper published at CEUR-WS under the CC-BY 4.0 license was republished by in a relatively unknown and new journal without consent by the author. What can we as academics do in such cases?
Well, in first instance the author (perhaps together with the editor of the volume where the paper appeared) should take initiative and contact the editorial board about the case. According to the CC-BY 4.0 clause, a re-publication is legal if credits the authors are given. This is a very broad license meant to maximise access to papers.
Besides the CC-BY legal framework, there are other norms and laws that the author can use to get the unwanted re-publication removed, if she or he wishes that.
First, the author is the copyright holder. No other person or organisation shall claim to hold the copyright unless they have legally obtained the copyright.
Second, if another person uses the content of the paper and remixes it and then publishes it under his/her name, then this may well be a case of plagiarism and should be dealt with accordingly.
Third, if the author name is not changed but the re-publication is without consent by the author, it may be a case of unethical academic behaviour by the editorial board. If there is an academic on the board (e.g. the chairperson), then contact this person and lay out the case. This person is also bound by the code of academic conduct. Demand that the unwanted republication of your paper is removed from the journal (if that is what you wish as copyright holder of the original paper). If the person does not answer or the answer is not satisfactory, then consider to escalate the case to the dean of the university/school where the chairperson or editorial board member is employed.
This is only my personal view and no legal advise.