The one penis policy, universally abbreviated to OPP, refers to an agreement in a CNM relationship where a woman is permitted to have sexual or romantic connections with other women but not with other men. The man she's partnered with retains exclusive access to her in relation to other men. The restriction does not apply in reverse: he may have connections with women without equivalent constraints.
It's one of the most debated arrangements in CNM communities, and the debate has sharpened considerably in the last few years. Understanding why it's controversial, and why it persists despite the criticism, tells you something real about power, insecurity, and the ways that heterosexual couple dynamics play out in non-monogamous contexts.
Where it comes from
OPP arrangements are most common when a heterosexual couple opens their relationship and the male partner is comfortable with his partner having connections with women but not with other men. The logic, where logic is offered, tends to run along a few lines: connections with women "don't count" in the same way; other men represent a different kind of threat; the male partner isn't threatened by women partners but would be by men.
Sometimes it's framed in terms of the partner's stated preferences, "she's mostly interested in women anyway", or as a temporary agreement while the relationship is new to non-monogamy. More often than it's explicitly articulated, it's an assumption that gets operationalised before anyone has examined it closely.
The criticisms
The CNM community's critique of OPP is well-developed and largely correct. A few of the main objections:
It's structurally unequal. The restriction applies to one partner and not the other, based on the gender of potential outside connections. The woman has her options constrained in a way her male partner's are not. Whatever reason is given for this asymmetry, it produces a relationship where one person has more freedom than the other, which runs counter to the stated ethics of most CNM frameworks.
It instrumentalises bisexuality. When a woman's connections with women are permitted because they're seen as less threatening or "not really counting," her bisexuality is being accommodated in a way that serves her male partner's comfort rather than genuinely acknowledged as real. The implicit message is that connections with women are acceptable because women aren't proper competition. This tends to be experienced as dehumanising both to the woman involved and to any woman she might connect with.
It's based on insecurity rather than ethics. The OPP exists because the male partner is specifically threatened by the idea of his female partner with another man, which is a feeling, not an ethical principle. Building a relationship structure around that feeling without examining it produces agreements that serve one person's anxiety at the expense of the other's autonomy.
It often signals broader control patterns. In practice, OPP arrangements frequently appear alongside other asymmetric rules, he has more freedom to initiate outside connections, her outside connections require more disclosure, her new connections are more closely monitored. The OPP is rarely the only place where the power imbalance shows up.
Why it persists
The persistence of OPP despite sustained community criticism has a few explanations.
One is simple: people opening their relationship for the first time bring the insecurities and dynamics of their existing relationship into the new structure. If the male partner is more anxious about male competition than female competition, which reflects fairly standard heterosexual jealousy patterns, the OPP can feel like a reasonable accommodation of that anxiety rather than a structural problem. "I'm not comfortable with X yet" is a legitimate starting point for negotiation; the problem arises when that temporary discomfort gets codified into a permanent rule that forecloses the question.
Another is that women in these arrangements sometimes genuinely prefer them, at least initially. If a woman is primarily interested in other women, a restriction on male partners may not feel limiting in practice. The philosophical problem with the OPP doesn't make it concretely restrictive for everyone it applies to. But preference in the moment and structural fairness are different questions, and it's worth both having.
A third is that the power dynamics that produce OPP in the first place also shape whether it gets questioned. If the male partner has more social, economic, or relational power in the relationship, the female partner may not feel that challenging the arrangement is a real option, even if she experiences it as limiting.
What a more honest version looks like
The underlying reality that OPP often tries to address, that one partner feels more threatened by certain configurations than others, is a legitimate starting point for conversation. The question is whether that conversation leads to a rule that limits one person's autonomy or to a mutual understanding that can be revisited.
A genuinely negotiated agreement that starts with "I'm not there yet with male partners" and includes a real plan for revisiting the question is different from an OPP that functions as a permanent structural limit. The former is a process; the latter is a policy that ends the conversation.
It's also worth asking directly whether the discomfort behind the OPP is about gender specifically or about something else, jealousy of emotional intimacy, insecurity about physical comparison, fear of the relationship changing in ways that feel threatening. Those underlying things are workable in ways that "other men are the problem" tends not to be.
The community's current position
OPP is broadly criticised in online CNM spaces and by most CNM writers, therapists, and educators. The criticism has shifted the conversation, it's now considerably less common to see OPP defended straightforwardly in poly communities than it was ten years ago, when it was treated as a fairly normal agreement for couples opening up.
What hasn't changed is the underlying dynamic that produces it. Heterosexual male jealousy of male competitors in an otherwise CNM relationship didn't become less common because the community decided OPP was problematic. What changed is that people became less likely to name it explicitly, which may just mean the same agreement shows up under different framings.
The critique matters, but it's more useful when it's diagnostic than when it's used as a litmus test for whether someone is "doing CNM correctly." People who are new to non-monogamy and working through genuine insecurity deserve engagement with the underlying feelings rather than the label. The goal is relationships that actually work for everyone in them, which sometimes means working through the discomfort that produced the OPP rather than either enforcing it indefinitely or abandoning the whole structure.