*497The terms of defendant's probation bar him from possessing firearms or illegal drugs. He contends that these conditions on his release are unconstitutionally vague on their face, because they do not explicitly define the state of mind, or mens rea, required to sustain a violation of probation. He requests modification of the conditions to convey explicitly that they apply only to knowing possession of the prohibited items. What we conclude is that the probation conditions already include an implicit requirement of knowing possession, and thus afford defendant fair notice of the conduct required of him. We therefore affirm the Court of Appeal.
I. BACKGROUND
Defendant LaQuincy Hall was convicted of possessing cocaine base for sale ( **796Health & Saf. Code, § 11351.5 ) and placed on three years' probation. As modified by the Court of Appeal to conform to the oral pronouncement of sentence ( *498People v. Mitchell (2001)
Defendant challenged these conditions as unconstitutionally vague for the first time on appeal. The Court of Appeal deemed this facial challenge cognizable as a question of law (In re Sheena K. (2007)
Other Courts of Appeal have taken a different view. (Compare People v. Moore (2012)
II. DISCUSSION
Penal Code section 1203.1 et seq. gives trial courts broad discretion to determine whether to grant an eligible defendant probation, and if so, what terms of probation will promote rehabilitation and protect public safety. (People v. Carbajal (1995)
In the context of conditions barring the possession, custody, or control of firearms, illegal drugs, and related items, revocation requires knowledge. The unwitting possession of contraband does not sufficiently establish backsliding by the probationer, nor **797does it sufficiently threaten public safety, to merit revocation without regard to the probationer's state of mind. On the other hand, revocation can be justified where the probationer knows of the contraband's presence and its restricted character because of what possession in such circumstances is understood to convey about an individual's plans or potential for further criminal activity, the probability of success of such activity if attempted, and the risks associated with such activity. Requiring such knowledge before sustaining a violation of one of the probation conditions at issue here would be consistent with the state of mind implicitly required for conviction by statutes criminalizing possession of illegal drugs (People v. Martin (2001)
Accordingly, a probationer who has possession, custody, or control of contraband willfully violates probation where the probationer has knowledge of the contraband's presence and its restricted nature, regardless of whether the item is criminal *565in itself, or merely related to criminality. And the Courts *500of Appeal have consistently so held. (E.g., In re Ana C. (2016)
The parties appear to be in agreement up to this point. Both sides recognize that defendant may not be deemed in violation of the firearms or narcotics conditions of probation if his possession or control of the prohibited items was unwitting. In other words, a probation violation can occur only if defendant knowingly owned or possessed these items or had them in his custody or control. Consequently, the issue presented here is not what state of mind is required to sustain a violation of probation, but the extent to which that state of mind must be expressly articulated in the probation condition itself to provide defendant with fair warning of what the condition requires. In defendant's view, the conditions at issue in this case are unconstitutionally vague and must be modified to state explicitly that knowing possession is required. The People respond that these conditions implicitly include a knowledge requirement already, rendering them sufficiently precise to afford defendant fair notice of what is prohibited.
Our analysis begins with the void-for-vagueness doctrine. This doctrine, which derives from the due process concept of fair warning, bars the government from enforcing a provision that "forbids or requires the doing of an act in terms so vague" that people of "common intelligence must necessarily guess at its meaning and differ as to its application." (Connally v. General Const. Co. (1926)
Given this legal backdrop, we conclude that the firearms and narcotics conditions *566are not unconstitutionally vague. California case law already articulates not only a general presumption that a violation of a probation condition must be willful, but also specifically provides that probation conditions barring possession of contraband should be construed to require knowledge of its presence and its restricted nature. (See generally In re Trombley (1948)
When a criminal statute similarly fails to expressly articulate the requisite scienter, we routinely rely on an analogous presumption. On occasion, and particularly for public welfare offenses, a statute will omit any reference to scienter, because no scienter is required. (Stark v. Superior Court (2011)
Defendant contends that the analogy between statutes and probation conditions is inapt. He points out that unlike statutes, probation conditions are "individualized," with wording that varies case by case. Defendant is correct: probation conditions encompass great diversity, in scope as well as phrasing. Where he is mistaken is in assuming that the requisite state of mind cannot lawfully be inferred from such conditions. Just as most criminal statutes-in all their variety-are generally presumed to include some form of mens rea despite their failure to articulate it expressly, so too are probation conditions generally presumed to require some form of willfulness, unless excluded **799" ' "expressly or by necessary implication." ' " (Jorge M. , supra , 23 Cal.4th at p. 872,
No one contends that the conditions challenged here expressly reflected *567an intention to remove the element of scienter, or that they implied the absence of any state of mind requirement to sustain a probation violation. To the contrary: case law has already made clear that knowledge of the contraband's presence and of its restricted nature is implicit in probation conditions restricting firearms and narcotics, regardless of any minor variations in the wording of those conditions. (People v. Rodriguez , supra , 222 Cal.App.4th at pp. 589-593,
Consider, for example, one of the most common probation conditions-the implicit condition to obey all laws. (See People v. Arreola (1994)
Defendant argues that Sheena K. nonetheless compels modification of the probation conditions challenged here. Not so. In Sheena K. , we approved the Court of Appeal's reliance on the vagueness doctrine to order modification of a probation condition barring the probationer from associating with " 'anyone disapproved of by probation.' " (Sheena K. , supra , 40 Cal.4th at p. 889,
Indeed, defendant's brief eventually concedes that "a potential solution" to the vagueness problem would be to "construe" the firearms and narcotics conditions as requiring knowledge of the contraband's presence and its restricted nature, as a number of courts have already done. Yet he continues to insist that modifying the conditions is a superior alternative. At core, what defendant seeks through modification is "absolute clarity" in the text of the condition itself, without the need to rely on "a judicial construction." But the question before us is not whether this degree of precision would be desirable in principle, but whether it is constitutionally compelled. As we have previously observed, the vagueness doctrine demands " 'no more than a reasonable degree of *568certainty.' " (Acuna , supra , 14 Cal.4th at p. 1117,
That degree of certainty is present in the conditions at issue here. Given the relevant case law, the firearms condition is properly construed as prohibiting defendant from knowingly owning, possessing, or having in his custody or control any handgun, rifle, shotgun, firearm, or any weapon that can be concealed on his person. So too with the narcotics condition, which is best read as **800proscribing defendant from knowingly using, possessing, or having in his custody or control any illegal drugs, narcotics, or narcotics paraphernalia, without a prescription. (Cf. Posters 'N' Things v. United States (1994)
III. DISPOSITION
The judgment of the Court of Appeal is affirmed.
We Concur:
Cantil-Sakauye, C.J.
Werdegar, J.
Chin, J.
Corrigan, J.
Liu, J.
Kruger, J.
We need not decide whether sustaining a probation violation requires a showing of willfulness where the probation violation poses a direct threat to public safety or otherwise frustrates the assumptions underlying the grant of probation, because this case does not appear to present such circumstances. (See United States v. Pinjuv (9th Cir.2000)
To the extent they concluded that an express knowledge requirement was necessary to prevent unwitting violations of possessory probation conditions, we disapprove In re Kevin F. (2015)
