To put an ad-blocker in an app, you have to reverse-engineer it. To do that, you'll have to decrypt and decompile it. That step is a felony under #Section1201 of the #DMCA, carrying a five-year prison sentence and a $500,000 fine. Beyond that, ad-blocking an app would give rise to liability under the #ComputerFraudAndAbuseAct (a law inspired by the movie Wargames!), under "tortious interference" claims, under trademark, copyright and patent.