I'm looking for crime statistics right now.
18 USC 2384 is colloquially known as "conspiracy to levy war against the US," and on its face, a conspiracy to blow up local cops does NOT meet the element of "against the US."
Meanwhile, check out the sister offenses, 18 USC 2383 and 18 USC 2385.
Title 18, Chapter 115 - Treason, Sedition, and Subversive Activities
Sec. 2385. Advocating overthrow of GovernmentWhoever knowingly or willfully advocates, abets, advises, or teaches the duty, necessity, desirability, or propriety of overthrowing or destroying the government of the United States or the government of any State, Territory, District or Possession thereof, or the government of any political subdivision therein, by force or violence, or by the assassination of any officer of any such government; or
Whoever, with intent to cause the overthrow or destruction of any such government, prints, publishes, edits, issues, circulates, sells, distributes, or publicly displays any written or printed matter advocating, advising, or teaching the duty, necessity, desirability, or propriety of overthrowing or destroying any government in the United States by force or violence, or attempts to do so; or
Whoever organizes or helps or attempts to organize any society, group, or assembly of persons who teach, advocate, or encourage the overthrow or destruction of any such government by force or violence; or becomes or is a member of, or affiliates with, any such society, group, or assembly of persons, knowing the purposes thereof -
Shall be fined under this title or imprisoned not more than twenty years, or both, and shall be ineligible for employment by the United States or any department or agency thereof, for the five years next following his conviction.
Several FALN members were convicted of seditious conspiracy on 18 February 1981. See Testimony of Gilbert G. Gallegos, National President, Grand Lodge, Fraternal Order of Police, on the offer of clemency by President William Jefferson Clinton to jailed members of the Puerto Rican terrorist organization, the Armed Forces of National Liberation (Spanish initials: FALN) before the Senate Committee on the Judiciary and the Senate Committee on Foreign Relations, Subcommittee on the Western Hemisphere, Peace Corps, Narcotics and Terrorism.
http://www.lawandsecurity.org/publications/TTRCComplete.pdf is an interesting summary of terrorism charges and convictions
My efforts at finding charging/conviction statistics are frustrating, so at this point I'm going to guess that 18 USC 2384 charges are very uncommon, as in they are filed at a rate of less than 1 per year. Other charges are more common, such as hundreds per year of material support for terrorism.
Reading those definitions only reinforces my concerns.
This administration could apply them to almost expression of anger directed towards them.
Actually, another poster here mentioned that the nutty black group in Miami, Seeds of David, was charged with seditious conspiracy. That would have been a couple of years ago, IIRC.