Regardless of the new security directives in place, you are never allowed to drink your own alcohol on board, whether it's purchased inflight duty-free or on the ground prior to boarding. I'm quite sure this is a regulation in place for all US-based carriers, and I'd guess is applicable to most international carriers as well. I'm unsure whether it's an FAA regulation, or directed by the individual carriers, but it is in place to give the crews a measure of control over alcohol consumption to ensure that passengers do not become drunk to the point that they pose a danger to themselves or others.

I've never tried (or witnessed) this, but if you can buy alcohol inflight duty-free, you may be able to give it to the FA and ask them to serve you out of that bottle.