This educational guide is based on the linked primary sources. It is not a Court publication, is not affiliated with the Court, and is not legal advice.
In brief
Overview
The case Tarrant Regional Water District v. Herrmann concerns the interpretation of an interstate water‑compact that governs how water can be allocated among states.
The Compact says each state may manage water rights under its own laws, but only as water is available under the Compact.
According to Ms. O'Connell, one side argues that any state law that conflicts with the Compact’s allocation should be preempted.
According to Ms. Blatt, the opposing side contends that the state’s authority can be exercised and does apply.
Background and question before the Court
Section 2.01 of the Compact preserves the application of state water law, allowing each state to administer water rights in accordance with its own laws, subject to water availability under the Compact.
According to Ms. O'Connell, the legal question is whether a state law that conflicts with the Compact’s allocation is preempted by the Compact.
Justice Breyer asked whether a mechanism exists to enforce such preemption, suggesting none is in place.
According to Justice Kagan, justice Kagan questioned Ms. O'Connell’s view, indicating uncertainty about accepting that argument.
Justice Scalia repeatedly asked “Where is this?” highlighting concerns about locating the relevant authority.
What each side argues
Petitioner (Tarrant Regional Water District)
According to Ms. O'Connell, if a state law conflicts with the allocation under the Compact, that state law is preempted.
Respondent (Rudolf John Herrmann)
According to Ms. Blatt, it can and does.
What happened at oral argument
According to Justice Breyer, justice Breyer: “I would have thought a mechanism would be set up to do that and there is none.”
According to Justice Kagan, justice Kagan: “Ms. O'Connell, isn’t that a reason why we shouldn't accept your basic view? I mean,”
According to Justice Scalia, justice Scalia: “Where is this? Where is this? Where is this?”
What the Court decided
Why it matters
Terms to know
No glossary terms are available for this guide.
Primary sources
Read the source materials on the official site or open the immutable repository copy used for this guide.
- c05cdcf61a14742c3692-r1-65ce80bc475305c4.pdforal argument transcript
Guide generated September 24, 2026. Automated validation accepted this version.