User blog comment:B214/Light Novel Volume 16 spoilers/@comment-162.202.198.72-20131029215449/@comment-216.203.80.125-20131112225020

If issei combines his demonic & dragon powers with SG. than it might work. Like how reverse doesn't work on combined powers, Nullification also might not work with combined powers.

Also Issei had forbidden power for SG (Longenious Breaker). Since its power is beyond SG.

Also there are holes in SG system. All powers that fall in this category might work against nullifier