Not anymore! These are allowed at least in the UK and in Germany (where I reside) now. It was not the case when I first moved here a few years ago, but read about how they're within code now. The problem I have is that they're not actually available anywhere that I've seen, and I doubt I'll find a plumber easily who will install one.
They are still forbidden in France, and not because of the code.
This is because the sanitizing stations are not ready for this kind of mash - they expect cleaner water + oil + larger particles. What they get instead is a substance that kills the bacteria in charge of the sanitization.