FWIW, in Spain we made our rules to say:
* The photos can be published using the [[Wiki Loves Monuments Upload
Wizard]], designed to help in the participation on this contest.
* Those uploading their photos not using this wizard must indicate their
participation manuall adding the code {{Wiki Loves Monuments 2016|xy}}
to the image page.
Also, a similarly designed point is:
* It is the participant responsibility to ensure that the photos are
tagged with a valid identifier…
(ie. if they didn't put the right identifier but someone else did for
them, that's ok, but they shall not rely on it)
Regards