Largely depends on the host, even in the same region.
From what I gather, there was a quality control issue with slugs in Canada, and they were banned there. To my knowledge, wars hosted by FA, K10, Pearson, Tank/Dumpster et al in the soutwestern ontario area are the only wars that ban slugs outright, and even then they've allowed our high-quality imported American darts on a case-by-case basis.
Here in Jersey, it entirely depends on who hosts. Mag7/Horsemen wars universally require slugs, as do the vast majority of LGLF events. Andtheherois doesn't have any hard restrictions on glue domes for NJNO, but I believe you are expected to use the lighter end of the weight spectrum and your darts have to be decent quality (not falling apart, fracturing on the tip, or being shaped in a grotesque or inhumane way) He also accepts slugs pretty much across the board. I think Redshot's PA wars and Chaos/Keo's DCNFs follow a pretty similar standard.
The only other areas I'm familiar with are Chicago (U3, not those other guys) and Southern Cali. U3 wars are currently slugs only, but may switch to their own special silicone darts in the future. Southern california wars, like Armageddon permit pretty much anything as long as Ice9 isn't using it.
Basically, what I would recommend is that you make a nice batch of slugs using Ryan's method
and just pay the extra $10 for the dart supply at Massacre. You can bring your slugs with you, and ask permission to use them, but be prepared to get denied. In my experience, even when I've brought my own darts to Canada they magically cease to feed properly though my hopper as I cross the border. If anyone is interested in studying this mysterious subtemperate dart shrink phenomenon, I might be persuaded to provide a nerfy research grant.
Edited by Langley, 21 February 2012 - 06:03 PM.