To modern scholarship, the presence of pseudepigraphical texts in the New Testament is a certainty. Almost half of Paul's letters were not written by Paul (though two or three of them may have been written by a close student of his views). The Letter of Judah is pseudepigraphical, written sometime in the late first century AD. The First Letter of Peter likewise was not written by its eponymous apostle. Instead, 1 Peter was written roughly contemporaneously with Judah.
If Judah and 1 Peter are pseudepigraphical, then there is no doubt that 2 Peter is, too.
Critical scholarship is essentially unified on the authenticity of 2 Peter, which is to say they nearly all agree it was written in the first half of the second century AD, about fifty to seventy years after Peter had been dead. Second Peter has borrowed from both Judah and 1 Peter in the course of writing his letter, and the pseudonymous author's clearest dependence on the traditions of the Book of Enoch is actually seen in the way he combines the corresponding passages from Judah and 1 Peter.
Judah // 1 Peter // 2 Peter
||And Enoch went and made a proclamation to
||For if God did not spare
The author of 2 Peter shows himself to be acutely aware of the Enochian literary traditions standing behind each passage, and so by combining them shows how integral that story is to his general theological background.
Second Peter 3.1 does refer to 1 Peter directly, but although 2 Peter never mentions the Letter of Judah or acknowledges his dependence on the earlier work, the author has actually plagiarized nearly the entire text of Judah. As you compare the parallels between Judah and 2 Peter, notice how Judah's clear echoes of 1 Enoch tend to become diluted and indirect in 2 Peter.
For example: The Book of Enoch uses the words deny, lord, and messiah; Judah uses deny, lord, and messiah, but also adds the word master; 2 Peter uses deny, but drops the lord and messiah shared by 1 Enoch and Judah, while keeping the master introduced by Judah.
This demonstrates that 2 Peter took from Judah, rather than the other way around. The point being that, by incorporating so much of the Letter of Judah (rather than inventing the material himself), the author of 2 Peter incorporates virtually all of the Enochian theology present in Judah.
In other words, the presence of Judah, 1 Peter, and 2 Peter in the New Testament equates to a tacit approval of the Book of Enoch's theology, even if the Book of Enoch was itself left out. Accepting those three pseudepigraphical letters as 'canon' while rejecting 1 Enoch would be like accepting the Revelation while rejecting the Book of Daniel. The Revelation owes so much to the Book of Daniel that the former could not exist as it does without the latter. Judah, 1 Peter, and 2 Peter are so dependent on 1 Enoch that these letters might not even exist without it.
Judah // 2 Peter
|May mercy, peace, and love be yours in abundance.||May grace and peace be yours in abundance in the knowledge of God and of Jesus our Lord.|
|For certain intruders have stolen in among you, people who long ago were designated for this condemnation as ungodly, who pervert the grace of our God into licentiousness and deny our only Master and Lord, Jesus Christ. Now I desire to remind you, though you are fully informed, that the Lord,
||But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive opinions. They will even deny the Master
|And the angels who did not keep their own position, but left their proper dwelling, he has kept in eternal chains in deepest darkness for the judgment of the great day. Likewise, Sodom and Gomorrah and the surrounding cities, which, in the same manner as they, indulged in sexual immorality and pursued unnatural lust, serve as an example by undergoing a punishment of eternal fire.||For if God did not spare the angels when they sinned, but cast them into Tartarus and committed them to chains of deepest darkness to be kept until the judgment; and if he did not spare the ancient world, even though he saved Noah, a herald of righteousness, with seven others, when he brought a flood on a world of the ungodly; and if by turning the cities of Sodom and Gomorrah to ashes he condemned them to extinction and made them an example of what is coming to the ungodly|
|Yet in the same way these dreamers also defile the flesh, reject authority, and slander the glorious ones. But when the archangel Michael contended with the devil and disputed about the body of Moses, he did not dare to bring a condemnation of slander against him, but said, 'The Lord rebuke you!' But these people slander whatever they do not understand, and they are destroyed by those things that, like irrational animals, they know by instinct.||especially those who indulge their flesh in depraved lust, and who despise authority. Bold and willful, they are not afraid to slander the glorious ones, whereas angels, though greater in might and power, do not bring against them a slanderous judgment from the Lord. These people, however, are like irrational animals, mere creatures of instinct, born to be caught and killed. They slander what they do not understand, and when those creatures are destroyed, they also will be destroyed, suffering the penalty for doing wrong.|
|They count it a pleasure to revel in the daytime.
|But you, beloved, must remember the predictions of the apostles of our Lord Jesus Christ; for they said to you, 'In the last time there will be scoffers, indulging their own ungodly lusts.'||This is now, beloved, the second letter I am writing to you; in them I am trying to arouse your sincere intention by reminding you that you should remember the words spoken in the past by the holy prophets, and the commandment of the Lord and Savior spoken through your apostles. First of all you must understand this, that in the last days scoffers will come, scoffing and indulging their own lusts and saying, 'Where is the promise of his coming? For ever since our ancestors died, all things continue as they were from the beginning of creation!'|
|But you, beloved, build yourselves up on your most holy faith; pray in the Holy Spirit; keep yourselves in the love of God; await the mercy of our Lord Jesus Christ that leads to eternal life. And have mercy on some who are wavering; save others by snatching them out of the fire; and have mercy on still others with fear, hating even the tunic defiled by their bodies.||Since all these things are to be dissolved in this way, what sort of people ought you to be in leading lives of holy conduct and godliness, awaiting and hastening the coming of the day of God, because of which the heavens will be set ablaze and dissolved, and the elements will melt with fire?|
|to the only God our Savior, through Jesus Christ our Lord, be glory, majesty, power, and authority, both now and into all eternity. Amen.||But grow in the grace and knowledge of our Lord and Savior Jesus Christ. To him be the glory both now and into the day of eternity. Amen.|