Cite as: 575 U. S. ____ (2015) 3 THOMAS, J., dissenting ically protected speech be suppressed at the will of an eggshell observer, cf. Cox v. Louisiana, 379 U. S. 536, 551 (1965) (“[C]onstitutional rights may not be denied simply because of hostility to their assertion or exercise” (internal quotation marks omitted)). There is thus no dispute that, at a minimum, §875(c) requires an objective showing: The communication must be one that “a reasonable observer would construe as a true threat to another.” United States v. Jeffries, 692 F. 3d 473, 478 (CA6 2012). And there is no dispute that the posts at issue here meet that objective standard. The only dispute in this case is about the state of mind necessary to convict Elonis for making those posts. On its face, §875(c) does not demand any particular mental state. As the Court correctly explains, the word “threat” does not itself contain a mens rea requirement. See ante, at 8–9. But because we read criminal statutes “in light of the background rules of the common law, in which the re­ quirement of some mens rea for a crime is firmly embed­ ded,” we require “some indication of congressional intent, express or implied, . . . to dispense with mens rea as an element of a crime.” Staples v. United States, 511 U. S. 600, 605–606 (1994) (citation omitted). Absent such indi­ cia, we ordinarily apply the “presumption in favor of scien­ ter” to require only “proof of general intent—that is, that the defendant [must] posses[s] knowledge with respect to the actus reus of the crime.” Carter v. United States, 530 U. S. 255, 268 (2000). Under this “conventional mens rea element,” “the de­ fendant [must] know the facts that make his conduct illegal,” Staples, supra, at 605, but he need not know that those facts make his conduct illegal. It has long been settled that “the knowledge requisite to knowing violation of a statute is factual knowledge as distinguished from knowledge of the law.” Bryan v. United States, 524 U. S. 184, 192 (1998) (internal quotation marks omitted). For