Passing the threat with legislation AND durable fiat makes it credible.

While one may quibble with the extent that Congress’ threats are credible in this instance, one thing that seems clear is that Congress’ threat is much more credible as part of the Clean Air Act than it would have been had Congress made the threat without passing legislation. Congress increased the risk that its threats would prove more than cheap talk because it is much more difficult to revisit legislation than to get in the way of Congress coming back to an issue at some point in the future.

What Congress seems to be doing here is precisely what Schelling advises us to do when trying to make a threat that seems patently incredible:

But it is hard to make it believed…. What we have to do is to get ourselves into a position where we cannot fail to react as we said we would—where we just cannot help it—or where we would be obliged by some overwhelming cost of not reacting in a manner we had declared…. Often we must maneuver into a position where we no longer have much choice left. This is the old business of burning bridges. If you are faced with an enemy who thinks you would turn and run if he kept advancing, and if the bridge is there to run across, he may keep advancing…. But if you burn the bridge so that you cannot retreat, and in sheer desperation there is nothing you can do but defend yourself, he has a new calculation to make (Schelling, 2008/1966, 43).

Careful institutional design can bind the government in two ways. First, it can make it costly (or even illegal) for an agency to escape a congressional command. Second, by providing an agency a nuclear option, one Congress may make it politically difficult for a future Congress to revisit its decision. Inertia and the difficulty of changing the status quo is part of Congress binding its hands. Additionally, if an enactment proves politically popular, it might be very difficult for a future Congress to change the enactment and to water it down. Depending on how difficult it is for a future Congress to back off, it may come close for a Congress to possess a power that is constitutionally is off limits: “one Congress, or one legislature, cannot bind a future Congress or legislature.”21 While no Congress can bind another Congress with a Gordian knot, one Congress can still make it difficult for another Congress to get free.

Binding ones hands is a reference to how Circe the Enchantress told Odysseus deal with the lure of the singing Sirens:

“To the Sirens first you shall come,” said she, “to the Sirens, who sit in their field of flowers and bewitch all men who come near them…. All round where the Sirens sit are great heaps of the bones of men. But I will tell thee, Odysseus, how thou mayst pass them.”

“When thou comest near put wax over the ears of thy company lest any of them hear the Sirens’ song. But if thou thyself art minded to hear, let thy company bind thee hand and foot to the mast. And if thou shalt beseech them to loose thee, then must they bind thee with tighter bonds. When thy companions have driven the ship past where the Sirens sing then thou canst be unbound.”

Congress may seek to delegate regulatory nukes as a way to bind its hands to the mast. When Congress seeks to coerce action through threats that seem against its interest or when otherwise it is on shaky political grounds, Congress may bolster those threats and raise the ante by passing legislation and then wait to see what happens. The more that it takes the decision out of the discretion of the agency, the bolder those threats are. This might be done, as it is in many environmental laws, by providing third parties the right to litigate and enforce the statues Congress passes. It may be done by providing clear language that does not give agencies wiggle room. It may be done by selecting agencies that are perceived tough or beholden to an interest that favors enforcement of the law. It may also be done by exploiting the symbolic power of taking a particular course of action, which leads us to a second but related reason Congress delegates power.