Is this something to do with EU legislation?

This was one thing the dealer mentioned but they also mentioned all sorts of things, some they redacted. It is something I have not come across before and the dealer has left it at that saying they have no further information for me.

Possibly the EU are trying to interfere in the UK car market and pressuring/threatening car manufacturers not to register cars. Maybe write to your MP, SMMT etc.

Sounds as if the car is an old model not compliant with current requirements and the manufacturer/importer has to apply for 'end of series derogation' from Vehicle Certification Agency - i.e. special permission to register the vehicle.

I assume that the dealer didn't tell you this when you agreed to buy it? Maybe that's why they're being less than forthcoming with information now. I assume that an old model is worth less than a current one.

Suzuki emissions average has financial penalties under EU regs

This is one reason for Suzuki buying Toyotas - Rav4 & Corolla and rebadging them as Across & Swace. If Suzuki sell a lot of the Toyota hybrids this will bring down the "average emissions" and mean less in the way of fines on the Suzuki range.

However Suzuki do not seem to sell many Across models - few dealers in Scotland seem to have more than a demo model - some chains have 1 demo and move it between branches. Mind you how many Suzuki buyers will want to spend £46K? - that is Lexus money!

The Swace has the 1.8 engine only - again much more expensive than the "normal" Suzuki.

Subaru do not have the same issues as they sell so few cars in Europe - they are regarded as "niche" car makers despite selling loads outside the EU e.g. US & Australia.