Yes, pretty much every serious venue is considering only papers with novel, unpublished research, so if you've published "that thing" already somewhere else then that disqualifies you from getting a well-ranked publication out of that piece of research, and it's strong disincentive to publish anything outside of the venues that 'count' for the purposes of evaluating you or your project goals.

In most cases there are no restrictions where you can publish, but you simply know the fact that evaluation committees will look down upon papers published in a venue that is not among the respected ones. Some institutions, and in some cases governments, have a white-list of venues that are considered worthy to publish, so sending a paper to a venue that is not on the white-list will get it evaluated with 0 points. And you will be looked down upon by your colleagues, if you have such papers in your CV.

Publishing the same stuff at several places is considered self-plagiarism, but probably this was not what was your question about.