Corpora
Six bodies of law, one parameter.
Every law endpoint takes corpus, and it defaults to statutes. The list is closed — anything outside it is a 400 bad_corpus — and which jurisdictions carry which corpus is answered live by /v1/law/coverage.
Pick the right one first
Most empty answers are a corpus mistake rather than a coverage gap. A Medicare condition of participation is a regulation, not a statute. A CMS survey tag is guidance. A deadline for filing a brief is a court rule. Asking the default corpus for any of them returns nothing, and nothing reads exactly like an absence.
# a CFR section — corpus=regulations, not the statutes default
curl -G "https://api.binding.law/v1/law/lookup" \
-H "Authorization: Bearer $BINDING_API_KEY" \
--data-urlencode "jurisdiction=us" \
--data-urlencode "citation=42-482.13" \
--data-urlencode "corpus=regulations"Statutes
Codified law as the jurisdiction publishes it, section by section. The default corpus: omit corpus and this is what you query.
Regulations
The Code of Federal Regulations in full, and state administrative codes. This is where agency rules live — not in statutes, which is the single commonest reason a search returns nothing.
Court rules
Rules of civil and criminal procedure, evidence, and appellate practice, as promulgated for each court. A rule that binds a court — not an instruction read to a jury, which is why the two are counted apart.
A rules row that governs filing typography, spacing, margins or length carries topics: ["format"], meaning the court filing-format registry at /v1/law/format has a structured reading of it.
Jury instructions
Pattern instructions as approved for use at trial, split to the individual instruction and carrying their official notes on use alongside rather than merged into the text a judge would read out. One corpus rather than one per set: civil, criminal and contract are publications of a single material class, and the set rides in the citation's structure.
Because the set is in the key, a bare number like 401.14 is ambiguous and answers no_edition_on_file with a didYouMean list rather than a guess. Federal circuit instructions use circuit jurisdiction codes: us-ca3, us-ca5, us-ca6, us-ca8, us-ca9, us-ca10, us-ca11.
Constitutions
The United States Constitution and the state constitutions, one row per section, current text. A constitution is amended by the people rather than the legislature and outranks the code, so it is its own corpus rather than a corner of statutes.
Agency guidance
Sub-regulatory agency material — interpretive guidelines and survey procedures. The CMS State Operations Manual, including the Appendix M hospice survey tags, and related manual and memo material.
This corpus, and only this corpus, is not binding law. Every response says so in its disclaimer. Do not let an agent present guidance as a regulation.
Sentencing Guidelines
The United States Sentencing Guidelines Manual — one row per guideline section, one edition per November 1.
Held apart from guidance on purpose. A sentencing court must calculate the range under 18 U.S.C. § 3553(a)(4) and the commentary binds under Stinson, so this material cannot ride under a disclaimer that calls it non-binding.
Reading a citation key
Keys are normalized per jurisdiction and per corpus, and both the normalized key and the display citation are matched — so 768.28 and § 768.28, Fla. Stat. both resolve. Where a jurisdiction needs more structure than a number, it rides in the citation’s parts object on the way out.
Jurisdiction codes are lowercase. Most are the two-letter state code; us is federal, dc is the District of Columbia, and federal circuit material uses circuit codes such as us-ca9. Round-trip the exact citation.key a search hit gives you rather than reconstructing it — on MCP that value is also accepted under the argument name key for exactly this reason.
What the validity dates mean
temporalBasis rides on every coverage row and every served section, because the same two dates mean different things in different jurisdictions and pretending otherwise is how a point-in-time answer quietly becomes wrong.
When a jurisdiction puts material somewhere else
Wisconsin enacts its civil procedure, evidence, criminal procedure and appellate procedure as statute chapters; its court rules are the Supreme Court Rules, keyed under wi rules as scr-20:1.7. Asking wi rules for a procedure section such as 802.08therefore misses — and the message points at the statute chapters that do carry the text, rather than stopping at “we do not have it” and sending you away from material we hold.
The live matrix is the authoritative account of what is queryable today. The coverage page renders it, and /v1/law/coverage serves it to your code, free and without a key.