Via the Corner, note that he makes no actual argument to support the distinction. It’s an empty assertion, of necessity. Absolutely he can seize lawmaking power from Congress to amnestize five million people; absolutely not may a Republican president try the same move on taxes. Why? The honest answer, that amnesty serves the left’s agenda whereas lower taxes undermine it, wouldn’t fly even among a media that’s straining to defend him so he’s forced to dismiss Stephanopoulos’s hypothetical and leave it at that.

The closest he comes to an explanation is in saying that prosecutorial discretion is okay for immigration because “we are not even close to being able to deal with the folks who have been here a long time.” But that’s not true. The Gang of Eight bill, passed by the Senate last year with Republican help, would have “dealt with” long-term illegals. The GOP establishment, John Boehner very much included, is desperate to reach out to Latino voters before 2016 with some sort of legalization bill; the trick is getting Democrats to agree to enough security improvements that conservative voters will kinda sorta tolerate the deal. That is to say, on the key policy that Obama wants — legalization — the Democratic and Republican leaderships are in sync. It’s the politics of passing it that are difficult. Compare that to, oh, say, tax reform, where not only are the politics of a deal difficult but there’s sure to be a policy gulf between Republicans and Democrats even on basic things like income tax brackets. If the sine qua non of executive power grabs is congressional paralysis, the argument for seizing power over taxes is much stronger than it is for immigration.

But get used to this sort of “reasoning.” Lefties had their chance to convince Obama not to open Pandora’s box on separation of powers; now that it’s open, arguing over why it should or shouldn’t be opened again will be a regular feature of partisan debates. Vox.com, one of O’s more reliable water-carriers, has already begun arguing preemptively that a Republican president couldn’t possibly use an executive order to limit tax collection. Sean Trende takes that case apart in a few quick paragraphs:

Prokop’s first scenario involves President Rick Perry declaring that there would be a 17 percent flat tax and instructing the Justice Department to defer all prosecutions. He cites former Solicitor General Walter Dellinger’s response: “no president can relieve any one American of a statutory obligation to pay taxes. The next president can come collecting– and interest and penalties will be accruing until he or she does.” First, Obama’s action suffers from the same shortcoming. In theory, nothing legal stops a future Republican president from using the list of individuals signed up for work permits as a sort of “illegal immigrant database” to help focus deportations. In fact, the statute of limitations for most audits is three years, with a practical limit of less than that. Also, just as practical limitations would probably prevent a future GOP president from deporting these individuals, so too would a future Democratic president find it difficult to collect on millions of three-year-old tax bills. But more importantly, when President Perry walks out the door, he can issue a pardon for everyone who avoided taxes during his presidency. Prokop just sort of breezes past this possibility, asserting that it would provoke a massive public outrage. But what would an outgoing President Perry care? He would do so after the next presidential election. Moreover, millions of Americans would have enjoyed substantially lower tax rates for either four or eight years. The incoming president would have a hard time reverting to a 28 percent middle-class tax rate (this assumes that there would be more winners than losers under the executive order).

Precisely. Once presidents start handing out momentous political goodies to key constituencies like amnesty, their successors will be loath to antagonize those constituencies by rescinding the orders. If Scott Walker narrowly wins in 2016 with a larger than expected share of the Latino vote, e.g., 35-40 percent or so, how eager will he be to cancel Obama’s amnesty knowing he’ll probably need the same margin in 2020? If Walker issues an executive order imposing a flat tax of 17 percent, as Trende imagines, how eager would the Democratic nominee in 2020 be to rescind that order completely? They’d be pressured by lefties to do something to restore the old status quo, but I’d bet they’d end up proposing some sort of compromise rate instead — for instance, 22.5 percent, halfway between Walker’s flat-tax rate and the current 28 percent middle-class rate. And of course Congress would be reluctant to deviate too far from the president’s rate if it ended up passing a tax-reform bill of its own, simply because there’s always political peril in disappointing Americans’ expectations. I think we’ll end up with something similar on immigration if a Republican is elected next year — a new executive order that reduces (a little) the scope of Obama’s amnesty order but doesn’t rescind it entirely. That’s why this precedent is so dangerous. Even though executive orders are technically temporarily, the more they’re used to make sweeping changes to hot-button policy, the more permanent they’ll end up being as actors on both sides decide it’s too risky to tinker further with the status quo. In 20 years, what will still be left in Pandora’s box?