We used to have some form of this, but IIRC it was broken in some way and eventually removed. I can't find when it was added/removed. It's probably fine to try again with the more modern codebase that we have today.

We do have about 50 files per day in https://commons.wikimedia.org/wiki/Category:New_uploads_without_a_license , which are uploaded without a license. The files are tagged by a bot which looks for files not transcluding {{License template tag}} template. A better way would be to prevent users from uploading such files, or guide them through the process of choosing a license template.

Change 309384 had a related patch set uploaded (by Matthias Mullie):
Verify license tags for custom licenses

https://gerrit.wikimedia.org/r/309384

In T140903#2480363, @matmarex wrote:

We used to have some form of this, but IIRC it was broken in some way and eventually removed. I can't find when it was added/removed.

For future reference, this was done in ebdc2934701363521c97c6c803b821349a18d7b2 (https://gerrit.wikimedia.org/r/#/c/158589/). The old code checked that the template used is categorized in https://commons.wikimedia.org/wiki/Category:License_tags.

Change 309384 merged by jenkins-bot:
Verify license tags for custom licenses

https://gerrit.wikimedia.org/r/309384

Note that this is not done yet, a small configuration change is required. Without it, the patch only checks that any template at all is used in the custom license (it just looks for '{{' and '}}'), license validation is not enabled by default.

Change 312854 had a related patch set uploaded (by Bartosz Dziewoński):
mw.UploadWizardLicenseInput: Parse license templates as if they were used on a file page

https://gerrit.wikimedia.org/r/312854

I tried to compare the differences in behavior between the old code and the new code. The following templates, which would be accepted per the old rule (categorized in https://commons.wikimedia.org/wiki/Category:License_tags or subcategory), will be rejected per the new rule (do not transclude https://commons.wikimedia.org/wiki/Template:License_template_tag):

1. Template:ACCovers
2. Template:AELG
3. Template:Attribution-TRGov-Military-Coast Guard
4. Template:BDA-Scan
5. Template:Biblioteca Museu Víctor Balaguer-cooperation
6. Template:Cc-non-compliant
7. Template:CC-self
8. Template:Cornelius Richter permission
9. Template:Creative Commons copyright tags
10. Template:Currency
11. Template:Fredlyfish4 credit
12. Template:Gary Lee Todd permission
13. Template:Heiligenkreuz monastery permission
14. Template:Heirs-license
15. Template:Human body diagrams
16. Template:Häggström diagrams
17. Template:Images by H&S Medienservice
18. Template:Images by Svend Buhl
19. Template:License scope
20. Template:Lio1962p
21. Template:MAG permission
22. Template:MickStephenson2
23. Template:MikaVäisänen
24. Template:No rights reserved
25. Template:NoRightsReserved
26. Template:NTNU Universitetsbiblioteket
27. Template:Odia alphabet anime
28. Template:Oerknor-license
29. Template:Open Access Media Importer
30. Template:Patrimoni.gencat permission
31. Template:PD-Art license tags
32. Template:PD-art-70-3d
33. Template:PD-CERN-CMS
34. Template:PD-Cuba-Other
35. Template:PD-Cuba-photo
36. Template:PD-ineligible license tags
37. Template:PD-IRN
38. Template:PD-magic
39. Template:PD-pdsounds.org
40. Template:PD-Peta
41. Template:PD-subject
42. Template:PD-US-1923-abroad
43. Template:PD-US-statue
44. Template:Pennsylvania Department of Transportation permission
45. Template:Permission Arquitectura del Sol
46. Template:Photos by Bagn Bygdesamling
47. Template:Photos by Kulturhistorisk museum
48. Template:PixiUnoCredit1
49. Template:PossiblyPD
50. Template:Rcat
51. Template:Recitation-bot
52. Template:Riksarkivet (Norway)-media
53. Template:RodejongCredit
54. Template:RodejongCredit1
55. Template:RodejongCredit3
56. Template:Unicode-expat
57. Template:Vector-Images.com
58. Template:Volare
59. Template:WasMykola
60. Template:WasMykolaCreate
61. Template:WasMykolaMap
62. Template:WEF
63. Template:XGSC image
64. Template:Yatrides

In some cases this is okay (e.g. Template:PD-magic is not intended to be a real license template), in some cases it looks like it's not and the template should be fixed (e.g. Template:AELG).

Someone should go through this list before we perform the configuration change to enable this.

(The list was generated with the following script:

Change 312854 merged by jenkins-bot:
mw.UploadWizardLicenseInput: Parse license templates as if they were used on a file page

https://gerrit.wikimedia.org/r/312854

@matmarex I just foud your post from Sep 26 2016, 5:46 PM. The list you produced contains templates which should not be considered as copyright tags, despite how they are categorized. The test for presence of {{License_template_tag}} is used by at least 2 daily queries populating Category:New_uploads_without_a_license and Category:Media_without_a_license:_needs_history_check you can pick daily into the first category to see files that your change would (hopefully) prevent from uploading.

By the way, an alternative to checking for {{License_template_tag}} is to look for machine-readable_markers_to_copyright_templates used by media viewer etc. All files missing them are magically added to Category:Files_with_no_machine-readable_license by some software (not a template) which Commons users have no control over . We do not work with those much since I do not think you can query for them in the database, but looking if template provided has those markers when fully expanded would be another way to tell copyright templates from other templates.

OK, I guess we should go ahead with the configuration change to enable this, then. Thanks.

Change 318518 had a related patch set uploaded (by Bartosz Dziewoński):
Verify license tags for custom license in Commons' UploadWizard

https://gerrit.wikimedia.org/r/318518

Change 318518 merged by jenkins-bot:
Verify license tags for custom license in Commons' UploadWizard

https://gerrit.wikimedia.org/r/318518

Mentioned in SAL (#wikimedia-operations) [2016-11-14T14:40:54Z] <zfilipin@tin> Synchronized wmf-config/CommonSettings.php: SWAT: [[gerrit:318518|Verify license tags for custom license in Commons UploadWizard (T140903)]] (duration: 00m 47s)