In United States v. O'Brien, 391 U.S. 367, 88 S. Ct. 1673, 20 L. Ed. 2d 672 (1968), the Court dealt with incidental restrictions on free speech occasioned by the exercise of the governmental power to conscript men for military service. O'Brien had burned his Selective Service registration certificate on the steps 416 U.S. at 411 of a courthouse in order to dramatize his opposition to the draft and to our country's involvement in Vietnam. He was convicted of violating a provision of the Selective Service law that had recently been amended to prohibit knowing destruction or mutilation of registration certificates. O'Brien argued that the purpose and effect of the amendment were to abridge free expression and that the statutory provision was therefore unconstitutional, both as enacted and as applied to him. Although O'Brien's activity involved "conduct" rather than pure "speech," the Court did not define away the First Amendment concern, and neither did it rule that the presence of a communicative intent necessarily rendered O'Brien's actions immune to governmental regulation. Instead, it enunciated the following four-part test: "(a) government regulation is sufficiently justified if it is within the constitutional power of the Government; if it furthers an important or substantial governmental interest; if the governmental interest is unrelated to the suppression of free expression; and if the incidental restriction on alleged First Amendment freedoms is no greater than is essential to the furtherance of that interest." Id. at 377, 88 S. Ct. at 1679.