Problem: Peter affirms in this passage that God cast the fallen angels “down to hell and delivered them into chains of darkness, to be reserved for judgment” (cf. Jude 6). However, it is evident from the NT that demons roam freely over the earth, oppressing and even possessing people (cf. Matt. 12:22; 17:14–17; Acts 16:16–18; Rev. 16:14).
Solution: There are two basic explanations of this apparent contradiction. First, it is possible that Peter is speaking of the official and ultimate destiny of fallen angels (demons), not their actual and immediate status. That is, while they are already sentenced by God to eternal damnation, they have not yet actually started serving their term. Nonetheless, they know their time is coming (Matt. 8:29; Rev. 12:12).
Second, these passages may be speaking of two different classes of fallen angels, some already in chains (2 Peter 2:4) and the rest yet loose. Some believe Peter is referring to the “sons of God” (angels) of Genesis 6 who instigated intermarriage with women just before the Flood, since the very next verse refers to Noah (v. 5). If so, then this may account for why these particular angels are already in chains (so they cannot repeat their feat), as opposed to other demons who are loose.
“For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;
(2 Pet 2:4)”