Citations to the United States federal and state constitutions are denoted by “U.S.” or the abbreviated name of the state (as indicated in T10.1, p. 312), respectively, and the abbreviation “Const.” or “Const.” depending on the document type.
Abbreviate the subdivisions of constitutions, such as articles and clauses, according to T16, pp. 327-28. For foreign constitutions, see R20.4, p. 192.
Additionally, there are some examples on The Bluebook's Quick Style Guide.
For both the Whitepages and Bluepages, do not use a short citation form other than id. for constitutions.
The Style Manual, at 76 contains a minor exception to The Bluebook rules for constitutions, where a comma appears after the abbreviation “Const.” or analogous part.
U.S. Const. art. I, § 9, cl. 2.
U.S. Const. amend. XIV, § 2.
U.S. Const. pmbl.
U.S. Const. art. III, §§ 1–2.
La. Const. art. X, pt. IV.
N.Y. Const. art. I, § 9, cl. 2.
Tex. Const. art. 1, § 3.
U.S. Const. art. I, § 8, cl. 10.
U.S. Const. amend. XIIII, § 3.
Mich. Const. art 6, § 1.
Wash. Const. art. I, § 32.
U.S. Const., art. I, § 9.
Ill. Const. 1970, art. I, § 9.
Ill. Const. 1870, art. VI (amended 1964), § 1.