⚡ 10-Second Rule
Even when Congress stays silent, a state can't wall off trade to protect its own businesses from outsiders.
🧒 ELI-10 Scene
Six neighborhoods run one giant weekend bake sale together. The whole point is one open market: more bakers, more customers, better cookies for everyone. Then Pinehill posts a sign at its tables: "Only Pinehill bakers sell here. Outsiders pay triple." Nobody in charge of the bake sale said Pinehill could do that. The sign breaks the deal everyone joined, so it comes down. But notice the difference when Pinehill itself goes shopping. If Pinehill buys two hundred cupcakes for its own block party, it can choose Pinehill bakers. A buyer picking its own sellers is not the same as a gatekeeper blocking the market.
⚖️ Actual Rule
The Commerce Clause, by negative implication, limits state regulation of interstate commerce even absent congressional action. A state law that discriminates against interstate commerce — on its face, in purpose, or in practical effect — is virtually per se invalid; it survives only if the state shows a legitimate local purpose, unrelated to economic protectionism, that cannot be served by reasonable nondiscriminatory alternatives. City of Philadelphia v. New Jersey, 437 U.S. 617 (1978); Maine v. Taylor, 477 U.S. 131 (1986). A nondiscriminatory law that incidentally burdens interstate commerce is judged under Pike v. Bruce Church, Inc., 397 U.S. 137 (1970): it "will be upheld unless the burden imposed on such commerce is clearly excessive in relation to the putative local benefits." Three escape routes exist: (1) the market-participant exception — a state buying, selling, or hiring with its own resources may favor residents (Reeves, Inc. v. Stake, 447 U.S. 429 (1980)); (2) congressional authorization — Congress may consent to state laws that would otherwise fail; and (3) favoring state and local government entities performing traditional public functions, such as publicly owned waste facilities (United Haulers Ass'n v. Oneida-Herkimer Solid Waste Management Authority, 550 U.S. 330 (2007)).
ELI-10 translation: state rules that pick on outside trade almost always fall, unless the state is just shopping, Congress said yes, or the state favors its own public services.
🔍 Ask These Questions
- Does the state law treat out-of-state goods or businesses worse — on its face, in purpose, or in effect? (Does the rule pick on outsiders?)
- If it discriminates, is there a legitimate non-protectionist purpose with no nondiscriminatory alternative? (It almost always dies — protecting hometown wallets never counts.)
- If it treats everyone alike, does the burden on interstate commerce clearly outweigh the local benefits? (Weigh the harm to outside trade against the local good.)
- Is the state acting as a market participant — spending its own money as buyer, seller, or employer? (A state shopping with its own wallet can pick favorites.)
- Did Congress authorize the discrimination? (Congress can bless what its silence would forbid.)
- Does the law favor a government entity doing a traditional public job? (Steering trash to the town's own dump differs from steering business to the town's companies.)
⚠️ Bar Trap
Exam language: Examiners bury the market-participant exception: the state is operating a state-owned cement plant, funding its own construction projects, or buying supplies, yet the answer choices invite full discrimination analysis. The mirror trap: a facially neutral statute whose practical effect falls almost entirely on out-of-state firms is treated as discriminatory, not as a Pike balancing case.
ELI-10: First ask what hat the state wears. A shopper can play favorites; a rule-maker cannot. And a rule that looks fair but only ever hurts outsiders is not fair.
🧪 Question
The state of Alcorra enacts a statute prohibiting the sale within Alcorra of landscaping mulch produced outside the state. The legislative history shows the statute was passed after Alcorra mulch producers complained that cheaper out-of-state mulch was, in the sponsor's words, "driving our hometown industry into the ground." An out-of-state mulch producer that previously sold forty percent of its output to Alcorra retailers sues, claiming the statute is unconstitutional. Alcorra defends the statute as an exercise of its police power over land use and horticulture.
Is the statute constitutional?
(A) Yes, because regulation of landscaping materials falls within the state's traditional police powers. (B) Yes, because Alcorra is a participant in the mulch market and may favor local producers. (C) No, because the statute discriminates against interstate commerce and Alcorra has shown no legitimate purpose that nondiscriminatory means could not serve. (D) No, because the statute violates the Privileges and Immunities Clause of Article IV by burdening out-of-state corporations.
Answer: (C). The statute facially bans out-of-state mulch, and its purpose is protecting local producers — the core evil the doctrine targets. Facial discrimination triggers virtual per se invalidity, and economic protectionism can never supply the required legitimate local purpose.
💡 Why the Wrong Answers Are Wrong
- (A) treats the police-power label as a trump; even genuine health or land-use goals must be pursued through nondiscriminatory means where available.
- (B) misapplies the market-participant exception — Alcorra is regulating private sales, not buying or selling mulch with its own funds.
- (D) reaches the right result through the wrong clause; corporations are not "Citizens" protected by Article IV's Privileges and Immunities Clause.
- ELI-10: The misconception is thinking a good-sounding reason saves a keep-out rule. If the rule blocks outsiders to help local sellers, the reason is the violation.
