i believe that the ONLY thing they can control (for certain) is their Roundel or BMW trademark. if the roundel is removed, its perhaps a different discussion. now with that being said, the big elephant in the room had their lawyers shut down some 3d printing of our friend Markos ... for something that didn't have their Roundel on it. If the design patents are expired, and their are no trademarks on the piece ... and if we haven't taken intellectual property to build something in a special way ... there is a chance. but the billion dollar mega company has a string of lawyers to bully their way thru.
I think BMW in the past may have had 3 arguments to not produce parts.
1. Economics of scale always applies, and
2. then there is the illegal use of protected logo's (the roundel) as Markos experienced.
3. A third argument could have been that BMW simply was not allowed by the German government to produce these parts. This has recently been solved however. What follows now is a difficult story, and I'm guessing that if this is shared by non-engineering / legal experts, details get lost quickly and versions of the story maynot resemble the actual arguments.
I'll explain: It has to do with technical rules to which automotive components parts need to conform. BMW followed rules that were generally applied in Europe since the 60's, and since have spread to the rest of the world as a sort of standardization. (Some countries choose to keep their own rules; hence the US models have different bumpers, front beams, side markers, ride height, smog equipment etc). A set of rules was in place in Germany when our e9's were produced, and these rules have evolved into much more stringent rules in place today. The technical rule for tail lights is the united nations regulation UN ECE Regulation 7 and Regulation 48. A car manufacturer has to show that the car conforms to all regulations before the model can be approved for road use by a government . (called the approval or homologation process, or 'zulassung' in German done by the KBA organization). If parts are approved, then the 'E' symbol is added to the part and a reference to the approval number. The 2 in 'E2' stands for approvals granted by Germany. E4 is the Netherlands, E1 is France for instance. Original seatbelts and exhaust for instance also show these 'E2' symbols.
Now if a manufacturer stops the production of the car, they also have the choice to stop the production of spare parts, and ask the government to withdraw the official approval for any technically controlled parts, such as the taillight. If BMW withdrew their approval for this part somewhere in the past, then they were officially not allowed by law to start up the production again. If they kept the approval 'dormant', they would have the possibility indefinitely.
Recently however the legal situation changed by the revision 3 of the 1958 agreement of the United Nations. (I'm actually in the UN office in Geneva now writing this, sitting next to the German government officials from ministry and KBA) In order to make it easy for emerging markets to start with vehicle regulations from scratch, industry is now allowed to make vehicle components again to old standards as these may be cheaper then the high specs used in the western world; cheaper meaning that countries may find it easier to put regulations in place for their citizens if the cost burden to their population isn't enormous. Countries could then limit if these 'old technical status' parts are allowed for sale or not.
So with this change, BMW has the formal right to reproduce parts to old technical regulations. Germany does not forbid the sale of these old spec parts.
what remains are the 2 other subjects; can they make money of our backs, and are they OK if we remake parts ourselves using their (protected) logo.
interesting article with more explantion (ironically from Hella...) here:
https://www.hella.com/hella-com/assets/media_global/673_Legal_Requirements_Brochure_HELLA_EN.pdf
