Eh, the internet sort of makes that law not 100% enforceable. There are plenty of online balloon shops (most of which cater to looners) that use really discreet packaging. One of the balloon shops I use puts a completely different business name on the shipping label and lists the package contents as "toys" or "electronics".
Hell, I used to live in a town where you'd get reported to the police if you tried to buy large quantities of balloons (Because people were using balloons to smuggle large quantities of drugs). I was able to avoid that problem by buying balloons online.
Frankly, though, a better version of that law would be a ban on using balloons outside. That would put a stop to balloon littering without potentially causing needless harm to people who use balloons responsibly.