The American Civil Liberties Union of Oregon says that Mayor Ted Wheeler's efforts to keep far-right protesters from holding more rallies in Portland is an unconstitutional violation of the First Amendment.

Wheeler this morning announced that he has asked the federal government to revoke permits for a June 4 "free speech" rally in downtown Portland, saying the city was raw and angry in the wake of two slayings on a MAX train Friday.

Wheeler's announcement today drew immediate criticism from civil-liberties advocates. Shortly before 2 pm this afternoon, the ACLU of Oregon released its statement, in a series of tweets.

"The government cannot revoke or deny a permit based on the viewpoint of the demonstrators," The ACLU said. "Period.

"It may be tempting to shut down speech we disagree with," the statement continued, "but once we allow the government to decide what we can say, see, or hear, or who we can gather with, history shows us that the most marginalized will be disproportionately censored and punished for unpopular speech.

"We are all free to reject and protest ideas we don't agree with. That is a core, fundamental freedom of the United States. If we allow the government to shut down speech for some, we all will pay the price down the line."

The mayor's spokesman, Michael Cox, said Wheeler was not trying to muzzle far-right speech—but to break up a scheduled altercation between the "alt-right" and antifascist groups. Those groups had been regularly confronting each other, even before the Friday slaying of two men who confronted hate speech on a Portland MAX train.

"The mayor is not seeking to limit the content of speech," Cox said on Twitter. "He is seeking to prevent violence."