Can a brewery in California fill any growler? There has been some confusion around the laws regarding "refillable containers" in California.  At times, I have been told that a brewery cannot refill another brewery's growler.  At other times, I have been told that a brewery may (or by their discretion, may not) refill.  I own growlers from at least 3 different breweries, and I have friends who have many more -- it makes sense to me that I should be able to take any clean container to a brewery which offers growlers, and have it filled.

What do the actual laws of California state, regarding who can refill and into what vessels?
They can, provided that they:


Cover up existing labels
Add their own label containing the brewery name, beer name, and abv.
Are a brewery (bars and retailers cannot).


You're not alone in being confused, though.  A lot of breweries didn't really know either, and as a result decided not to, just to be safe.

Further complicating the issue is that many breweries just don't want to, either because they make money on their growlers or because it's a pain to deal with the labeling when their bar is busy.

SFGate has a decent article for further reading.