Oats are one of the 'cereals containing gluten' as defined by the EU. They were included because they are normally contaminated with wheat flour, not because they intrinsically contain gluten. They contain avenin, a protein most coeliacs seem to be able to tolerate in modest doses, but 5% of whom may not. Nevertheless, oats are on the official list of allergens - and have been since a 2003 Directive.
Because of this, oats must be emphasised on labelling, in accordance with EU FIC 1169/2011, which came into full effect December 2014. ("14 allergens" law.)
A separate law - Commission Regulation 41/2009, effective since 2012, on the labelling of gluten free food - specified that oats could be labelled gluten-free if produced free from wheat contamination - at least to levels below 20 parts per million (20ppm) required by law.
Neither of these laws 'trumps' or over-writes the other. The first is about allergens present; the second is about gluten 'absent' - and is not an allergen law.
Although 14 allergens laws allow some labelling exemptions with regards to cereals containing gluten ...
... they only include glucose syrups, maltodextrins and distillates - as you can see - not gluten free oats.
An oat is a 'cereal containing gluten' - even when it's a gluten-free oat - because no law has decreed it otherwise.
And the consequence of that apparent paradox is this: a gluten free oat still has to be highlighted as an allergen on labelling.
It's not perfect, but the best confirmation of this I've found is from the FSAI. Scroll down to "How should gluten-free oats be labelled in a list of ingredients?"
Coeliac UK also acknowledge the correctness of emphasising all oats, regardless of GF status, in this question on their site.
I've contacted a selection of the free-from oaty producers with this question on and off over some months. This hasn't always gone down well. Of the responses I've had (not many), none would tell me who advised them on oat labelling.
This is not to name and shame, but inconsistency is confusing the consumer, so examples are important. The following are drawn from my own labelling inspections, that of bloggers, and the few responses received. My research was by no means exhaustive; I've not contacted many manufacturers.
Not emphasising ...
Nairn's are not emphasising their GF oats - although they said that "as some coeliacs are also intolerant to the protein avenin which is found in oats we do highlight this on our packs".
Neither are Rude Health (who told me they'd correct this if needs be, and I have to compliment them on their willingness to discuss the subject earlier in the year openly on social media).
Neither are Perkier. Trek bars, no. Nature's Path, no. Windmill Organics (Amisa, Biona) told me "gluten free oats are not an allergen", so I presume they don't.
Morrison's, earlier this year, were doing both, but I checked last week and they've now got it right on almost all products - except their mixed granola, which oddly was wholly non-compliant with new regulations, and still had a 'contains' box.
Tesco products looked correctly labelled (see cookies above). Delicious Alchemy too.
Udi's used to not emphasise, and told me several times that was correct. Some months ago, they quietly changed and now do.
I'm particularly impressed when small brands get it right. Take a bow, Most Marvellous Baking. (Page from their site shown below.)
What's the solution?
Because around 5% of coeliacs can't tolerate oats, and a few rare individuals are oat allergic, they should remain an allergen.
To me it's obvious: redefine oats as not being a cereal containing gluten, and make it an allergen in its own right, rather than within a group containing its cousins wheat, barley, and rye.
Manufacturers using oats would still need to emphasise this 15th allergen - but also add a precautionary warning - 'contains wheat traces' - when using non-GF oats. If oats are naturally free from gluten, should we not be working on the premise that they are GF, unless declared otherwise - and not the other way around?
As for the confusion surrounding emphasising, I guess that's one for the FSA to advise on and help resolve. To my knowledge, they have not issued any guidance, advice or statement specific to this particular query of emphasising gluten free oats on labels.