If it can be negatived, can it be positived?

From page 42 and 43 of Notes and Cases on the Revised Penal Code, 2012 Edition by Leonor D. Boado we find her using negative as a verb:

Here's what Garner's Dictionary of Legal Usage, Third Edition says about the word:

Now I asked in the title of this post whether it can also be positived. Boado thinks so when she says that "the criminal liability is not negatived because intent is present." And isn't that a double negative?