Can a published journal article be submitted to conferences?

Advice on this case is from a small number of COPE Council Members. Most cases on the COPE website are presented to the COPE Forum where advice is offered by a wider group of COPE Members and COPE Council Members. Advice on individual cases is not formal COPE guidance.

Ordinarily it would be fine to present the findings of an author's research at a conference whether or not the article had been submitted, accepted or published. Indeed, in many fields, it is common practice. In general terms, copyright law is about the original expression of ideas, but not the ideas themselves - so while it might restrict an author from distributing the paper at the session or reading it line-by-line (if copyright has been transferred to the journal), it would not prohibit the author from crafting a new presentation using the ideas from that manuscript. It would be sensible for the journal to clarify what the authors mean by presentation of the ‘full text’.  
 
That said, the answer is dependent on the terms of acceptance with the journal. Does the journal require authors to agree not to disclose the content in any format until after the paper is published? Is the author restricted from sharing the as-yet unpublished manuscript? It would certainly be wise for the authors to avoid sharing the unpublished manuscript with a conference committee to prevent mistaken duplicate publication. The editors should also think about what, if any, materials, figures, tables, etc, they are happy to have shared prior to publication, and in what format. We would advise formalising these decisions in a publicly-available policy which could also cover whether the journal considers conference presentations to count as pre-publication, if their copyright terms allow early use with respect to their copyright licence, and which version can be used.
 
The ICMJE advises that ‘Authors should also consider how dissemination of their findings outside of scientific presentations at meetings may diminish the priority journal editors assign to their work.’ It would also be good practice for the authors to state in the article that the results were presented in part (or in full) at xx conference.
 
In the interest of transparency we would also recommend that the authors declare to the conference organisers and session participants that the content of the presentation is based on a forthcoming article. Some conferences do not allow the presentation of findings that have already been published, even when the publication date lies between sending in the abstract and the date of the conference.