It doesnt say you cant divide a 40 litre tank into two 20 litre tanks does it? It just stops people keeping fish in a container i'd consider too small to keep beer in.
I love that! One problem, breeder related again. I hatch out angel spawns in a 10 gallon, & keep them in there for 2-3 weeks. Other breeders use 5 or 2.5 gallon tanks. There are reasons for using the smaller tanks, other than consuming beer. By trying to keep idiots from doing what idiots do, you are screwing a group of people who contribute greatly to aquatics. Don't jam yourself up trying to save idiots from themselves, they will find something else stupid to do.