The key to guaranteeing the 2nd Amendment is to look at its history.
https://www.youtube.com/watch?v=pLR2yfhhPBM&feature=youtube_gdata_player
https://www.youtube.com/watch?v=pLR2yfhhPBM&feature=youtube_gdata_player
This has been discussed many times in other threads too.
Gura and SAF have treated this as a civil rights ssue from Day 1