I first heard about cascara last year and wanted to try some. However I live in the UK and it was withdrawn from sale due to some confusion around "Novel Foods". The EU defines this as “food that has not been consumed to a significant degree by humans in the EU prior to 1997”.

There was for a while a bit of confusion with independent coffee shops if they could sell it and make drinks with etc. -

https://unitedbaristas.com/blog/insights/2017/03/the-cascara...

I think it's been resolved, but I can't find much online about it.