O’Brien Test (a form of intermediate scrutiny) (adopted by Supreme Court in United States v. O'Brien, 391 U.S. 367 (1968), a symbolic speech/expressive conduct case involving the burning of a draft card as a protest against the Vietnam War).

The O'Brien test is what is called a two-track test. Initially, when the government regulates a form of expressive conduct, the Supreme Court applies a 3-part test that is a version of intermediate scrutiny. However, if the government fails to satisfy the second part of the test, it must then satisfy strict scrutiny in order to justify its regulation. Part two of the test focuses on the government's reasons for regulating the conduct at issue.

This distinction was identified in Texas v. Johnson:
We must first determine whether Johnson's burning of the flag constituted expressive conduct, permitting him to involve the First Amendment in challenging his conviction. See, e.g., Spence v. Washington, 418 U.S. 405, 409-11 (1974). If his conduct was expressive, we next decide whether the State's regulation is related to the suppression of free expression. See, e.g., United States v. O'Brien, 391 U.S. 367, 377 (1968). If the State's regulation is not related to expression, then the less stringent standard we announced in United States v. O'Brien for regulations of noncommunicative conduct controls. If it is, then we are outside of O'Brien's test, and we must ask whether this interest justifies Johnson's conviction under a more demanding standard. A third possibility is that the State's asserted interest is not implicated on these fact, and, in any event, the interest drops out of the picture.
The O'Brien test in its entirety requires:

When speech and non-speech elements combine in the same course of conduct, the government can regulate the conduct if the regulation:

(1) furthers an important government interest;
(2) the interest is unrelated to the suppression of free expression; and
(3) is narrowly tailored to further the government’s interest (but the government need not utilize the least restrictive means).

If the government fails to satisfy the second part of the test, as occurred in Texas v. Johnson, it must satisfy a stricter test and show that it adopted a narrowly tailored, least restrictive means to accomplish a compelling interest.