In the US laws differ from state to state - I believe in California the growler needs to have the name of the brewer on them to be filled at the brewery.
In NY we have a lovely little rule: not only can you fill up at a bar/pub, but beer distributors/offies can install taps. Therefore, you get to enjoy things like this[/url:37bb26ni].
16, 32, and 64 oz containers, generally; fresh for a week or longer before opening if it's filled right to the top and capped properly; but no tasters at the beer store - that's a different license.
I'd be delighted to see this happen in Ireland.