18 U.S. Code § 2383. Rebellion or insurrection
Whoever incites, sets on foot, assists, or engages in any rebellion or insurrection against the authority of the United States or the laws thereof, or gives aid or comfort thereto, shall be fined under this title or imprisoned not more than ten years, or both; and shall be incapable of holding any office under the United States.
(June 25, 1948, ch. 645, 62 Stat. 808; Pub. L. 103–322, title XXXIII, § 330016(1)(L), Sept. 13, 1994, 108 Stat. 2147.)
18 U.S. Code § 2384. Seditious conspiracy
If two or more persons in any State or Territory, or in any place subject to the jurisdiction of the United States, conspire to overthrow, put down, or to destroy by force the Government of the United States, or to levy war against them, or to oppose by force the authority thereof, or by force to prevent, hinder, or delay the execution of any law of the United States, or by force to seize, take, or possess any property of the United States contrary to the authority thereof, they shall each be fined under this title or imprisoned not more than twenty years, or both.
(June 25, 1948, ch. 645, 62 Stat. 808; July 24, 1956, ch. 678, § 1, 70 Stat. 623; Pub. L. 103–322, title XXXIII, § 330016(1)(N), Sept. 13, 1994, 108 Stat. 2148.)
I think Lockbox gives the accurate information on why, in the present day, this isn’t a capital offense.
That said, give them 10-20 years in prison with people from MS-13.