Although Judge Barrett did not write this opinion, she did join it. It has been (rightly or wrongly) considered a significant indicator of her views on environmental issues, so I have included it.
Warmke is a 100-acre parcel of former farmland in Illinois. It is eleven miles away from the Little Calumet River, which is (factually) navigable. Orchard Hill began building houses on this land and, in so doing, altered its drainage so that thirteen acres became wetland. These thirteen acres drained into the Midlothian Creek, a tributary of the Little Calumnet River (but not itself navigable). As a result, when Orchard Hill asked the Army Corps of Engineers to confirm that Warmke was subject to the Clean Water Act, the Corps held that it was. [4-5]
The review process was “lengthy, contentious and complex.”  Suffice it to say that there were many hearings, appeals, and remands, during which the Corps identified numerous reasons why it considered the Warmke wetlands to fall within the scope of the Clean Water Act. [7-9] These reasons will be stated below. Orchard Hill then sought review from federal court, where Judge John Robert Blakey deferred to the Corps on its factual findings and conclusions and held that it had properly applied a legal exclusion. Judge Blakey therefore granted summary judgment to the Corps. [9-10]
Under the law that applied to the 7th Circuit at the time, the Corps had jurisdiction over wetlands if a significant nexus existed between those wetlands and navigable (in the traditional sense) waters of the United States, which was not necessarily satisfied by proximity to non-navigable tributaries of navigable waters. [5-6 and note 4 on page 6] The Court of Appeals was to reverse the Corps’ decision if that decision was unsupported by adequate evidence or was simply too implausible to be considered anything other than arbitrary or capricious. [10-11]
Judge St. Eve, writing for the Court of Appeals for the 7th Circuit, held that the Corps’ decision was unsupported by the record. Judge St. Eve found the Corps’ conclusion that construction at Warmke might pass pollution to the Midlothian Creek too speculative.  Judge St. Eve then opined that, although the Corps had concluded that the loss of the Midlothian Creek watershed would lead to flooding or would pollute the Little Calumet River, the Corps did not explain why the impact of losing only the Warmke wetlands would be substantial. [12-13] The Corps also ascertained that construction at the Warmke wetlands would cost wildlife its habitat but Judge St. Eve held that it had not explained why this had a significant nexus to the Little Calumet River. 
Judge St. Eve then held that the Corps had failed to introduce evidence that neighbouring wetlands were similarly situated to the Warmke wetlands, finding that none of the maps in the record showed the Corps’ claimed 165 wetlands adjacent to the Midlothian Creek or that other wetlands in the same watershed were adjacent to the same tributary. Judge St. Eve held that the Corps had waived its waiver argument by failing to present it to the district court (although, unlike Judge Barrett, Judge St. Eve did not worry about the distinction between waiver and forfeiture).  Judge St. Eve held that the Corps was indeed required to identify how each “similarly situated” wetland was indeed similarly situated, i.e., adjacent to the same creek. [15-16] Judge St. Eve then held that, because the Corps’ opinion was supported by inadequate reasoning and evidence, it was due no deference. [16-17]
Therefore, the Court of Appeals vacated the judgment and ordered the district court to remand to the Corps, so that it could reconsider its decision.
The Barack Obama Foundation sought to build the Obama Presidential Centre – a “presidential library” with a museum, auditorium, athletics centre, garden, and (of course) public library – on 19.3 acres of land in Chicago’s Jackson Park. [2-3, 21] Construction would have a significant impact on the park and surrounding lands and would impose financial and other burdens on Chicago residents. 
Protect Our Parks (and individual Chicagoans) sued to prevent the City from constructing the Centre. Judge John Robert Blakey granted summary judgment to the defendants on all claims. After the decision but before the appeal was completed, the government issued a report about the project’s environmental and other effects, which Protect Our Parks argued was new evidence that justified relief from the previous judgment. Judge Blakey denied that motion as well. The Court of Appeals for the 7th Circuit considered appeals from both decisions. 
Protect Our Parks argued that selling the land violated Illinois’ public trust doctrine, because the sale was tainted by favoritism and self-interest. [5-7] It also argued that the City had acted beyond its authority in entering an agreement that violated many provisions of state law.  On its own initiative, the Court of Appeals for the 7th Circuit ordered the parties to brief whether Protect Our Parks had standing to bring those claims. Although even the defendants argued that it did, the Court of Appeals disagreed. [4-5] Because Protect Our Parks lacked standing to bring these claims, the district court also could not re-consider its decisions on them, whatever the contents of the federal government’s report. [22-23]
Protect Our Parks (which was represented by, among others, Richard Epstein) argued that federal courts in Illinois, applying federal standing doctrine to Illinois decisions interpreting the public trust, had found standing. [POP Brief at 1-4] Judge Barrett opined that whether the plaintiffs would have standing in state court was not relevant, because standing in federal courts was an issue of federal law. [7-10] Protect Our Parks further argued that it had standing because the construction would damage the Park, which would harm the plaintiffs’ fraction of the public’s ownership of the Park. [POP Brief at 4-7] Protect Our Parks therefore argued that it had standing under principles of equity, as when share-holders have standing to sue a corporation. [POP Brief at 10-11] Judge Barrett held that, under federal law, Protect Our Parks did not have standing because it was not harmed. She interpreted POP as arguing that it had standing because the Park would be damaged, which was not harm to the plaintiffs themselves. [10-11] Although harm to the Park could have given rise to standing, by interfering with the plaintiffs’ use of the Park and reducing their enjoyment of it, Judge Barrett found they had not made this argument. [Note 1 on page 9]
Finally, the defendants argued that the plaintiffs had standing because among them were Chicago tax-payers, an argument that the plaintiffs had successfully made in district court. [11-12 ] Individual plaintiff Maria Valencia was a tax-payer, although this was not proved to be true of Protect Our Parks. [Note 2 on page 11] Judge Barrett opined that municipal tax-payer standing was out-dated and that the Supreme Court should overturn it but was bound to apply the doctrine in this case. [12-15 and note 3 on pages 13-14] Judge Barrett held that the elements of municipal tax-payer standing were not met. The Obama Foundation would pay for the construction of the Centre; the City, for preparatory work and construction of athletic facilities.  The plaintiffs had only argued that the construction itself was illegal, which meant that the City would not be paying for the allegedly illegal activity. [15-17] Additionally, Chicago had substantial revenue from sources other than taxation, and the plaintiffs had not demonstrated that the City would use tax revenues to pay for those aspects of the project. 
Protect Our Parks did have standing to assert its claims under the U.S. Constitution. [18-20 and not 4 on page 19] It claimed that the City had taken its property in violation of the Takings Clause of the Fifth Amendment and the Due Process Clause of the Fourteenth Amendment. Protect Our Parks claimed that, under Illinois’ public trust doctrine, it had a beneficial interest in the use of the Park that was a property interest.  Even if this argument held up, that property interest would not necessarily be one protected by the Constitution. [Note 5 on pages 20-21] Judge Barrett quickly concluded, however, that Illinois case-law clearly established the lack of any such property right.  Judge Barrett also held that, under Kelo v. New London, a city’s transfer of property to a private party for a public purpose was a permissible “public use” and was entitled to deference.  Judge Barrett also held that Due Process was satisfied, because approving the Centre had required multiple legislative decisions that had all taken place after public hearings. [21-22]