Forcing to list a co-author that did not contribute after publishing We published a paper, me as first and corresponding author. There was a technician who repeatedly refused to work, did useless measurements after having been forced, which he never evaluated and basically said &quot;help yourself&quot;, never had a look at the publication during working on it, and now tries to force the group leaders to be included as co-author afterwards by lying about his contributions (still, he would have done no intellectual work but was pipetting down my protocols). Data integrity steps are not provided by the institute, so everyone could copy measurement files from the shared server. The group leaders want me to give in although they agreed with me on the phone, just because they fear more consequences from him than from me, since I was nice so far. Now I don't see why I should constantly reward such a person.

The paper is published. They agreed. Can they even force me if I (and another co-author) say no?
Would - by your experience - the journal be willing to amend at all?
Can he/they force me legally? I am not even employed there anymore.
Do I have to prove anything after publication? Can someone claim data from a shared server anyway? Is it my turn to (re)act?
Would you do some &quot;preparing steps&quot; from my side if not willing to give in?
Do you have any advice from former experience?

Kind regards and thanks for any help!
You might take a look here; and as for a more detailed response, let me focus on this one question:

Would you do some &quot;preparing steps&quot; from my side if not willing to give in?

You could ask everyone to tell you which contributions they offered based on the Contributor Roles Taxonomy (CRediT). And make sure that the CRediTs are visible in the publication as well.
On the one hand, it is possible that they will hesitate to point out their contribution in case they do not find anything worthwhile to pick from CRediT. On the other hand, you might actually end up finding one minuscule contribution of that co-author that does merit a mention according to CRediT. The &quot;objectified&quot; nature of CRediT might help to resolve such conflicts.
And if you have the CRediTs published as well, then the readership will at least know the variation in efforts of each co-author.