I actually looked up the filings for the (which is incredibly simple, perhaps the ACLU can learn to use Google).
NEMLEC is a charity for a couple counties of police forces in MA. They have golf outings and other things, to benefit police officers and their families, activities that are completely innocuous.
I guess what the ACLU got their panties in a bunch about is that the organization also acts as a central point of contact for SWAT training/ purchases in the region.
So... a group of police, are setting their training calendars together so they can have a training session with more people at one time so they can save money on instructor costs. And they are buying stuff in bulk to reduce their costs.
The ACLU needs to do some homework and find a more relevant problem to harp on.
ALSO, NEMLEC had their corporation status involuntarily revoked in 06-18-2012, so the whole 501(c)(3) thing is a moot point. They aren't an entity anymore, they can't claim 501(c)(3) anymore, even though that never mattered in the first place.