There's a reason the saying "Selective enforcement of the law is the first sign of tyranny" has teeth.
It's because it turns the rule of law and equality before the law into a system of feudal patronage and indulgences. If a state or organization can just get a waiver from a law then that gives them an unfair advantage, and indebts them to the man that granted said waiver.
At least Obamacare had provisions for waivers (which were generously doled out to faithful supporters). But now Obama's taken it upon himself to deem where No Child Left Behind is applicable... without even a legal fig-leaf.
And of course, the consequences of a Lord of the Flies style, whimsical executive without any checks and balances isn't something the Left apparently worries about.
At least when their guy's in office. Majorities of liberal Democrats now support drone strikes, keeping Gitmo open. Well, well, isn't that convenient.