By Michael Phillips | Father & Co.
Illinois lawmakers spent this spring writing a ten-factor, best-interest-style test into law for companion animals — a term the statute defines broadly enough to reach not just dogs and cats but horses. Effective January 1, 2027, House Bill 4540 — the Companion Animal Custody Equity Act, known in the press as “Rosie’s Law” — lets a court weigh caregiving history, emotional bonds, stability of environment, and continuity of routine before deciding who keeps a companion animal in a possession dispute. It does this regardless of whether the two people fighting over the animal were ever married. Unmarried couples, roommates, and former partners now get the same well-being-centered analysis that, until now, only divorcing spouses could invoke under the state’s 2017 pet custody statute.
Set next to how Illinois treats an unmarried parent seeking time with an actual child, the comparison is not flattering.
What HB 4540 Actually Does
The bill amends Illinois’s replevin law — the part of the Code of Civil Procedure governing recovery of wrongfully held property — rather than creating a new family-law cause of action. As enacted, it adds two new sections to 735 ILCS 5: Section 19-130, which lays out the well-being factors, and Section 19-106.5, authorizing temporary orders while a case is pending. It also amends Section 19-101 to define who can bring the claim in the first place.
That definitional piece matters as much as the factor list. Under the amended Section 19-101(c), “parties” to a companion-animal replevin action include not just owners but domestic partners, former partners, cohabitants, fiancés, or roommates — but only “if shared responsibility for the care of the companion animal can be demonstrated.” There is a threshold here. It’s just a factual one, resolved with the kind of evidence a court can weigh immediately — vet records, testimony about who fed and walked the animal — rather than a separate legal proceeding someone has to complete before that evidence is even admissible.
Once that threshold is cleared, Section 19-130(a) lets a court weigh the animal’s well-being “regardless of the legal status of the parties” — broader language than simple marital status, covering the full range of relationships the law defines. The evidentiary list runs ten items: daily caregiving history; feeding, grooming, veterinary, and training involvement; financial contributions to the animal’s care; emotional bonds between the animal and each party; stability and continuity of living environment; safety considerations and past conduct; witness testimony; the animal’s age and vulnerability; continuity of routine; and ownership documentation, which the statute specifies “may not be determinative on its own.” Section 19-106.5 separately authorizes temporary possession or caregiving orders, including limited visitation, while a case is pending, and animals ten years or older get additional weight given to continuity of environment and stress minimization.
None of this depends on the parties having been married. It depends on whether shared caregiving can be shown.
The bill — now Public Act 104-0613 — passed the Illinois House 72–38 in April 2026, then the Senate 52–7 the following month, and was signed by Governor JB Pritzker on July 24, 2026. Its sponsors framed it explicitly as closing a gap the 2017 divorce-code provision left open: two people who never married had no proceeding to attach a pet-possession claim to, and therefore no mechanism for a court to weigh a companion animal’s welfare at all. HB 4540 gives them one, gated by proof of caregiving rather than a marriage certificate.
“None of this depends on the parties having been married. It depends on whether shared caregiving can be shown.”
What the Illinois Parentage Act Does
Illinois children born to married parents get a legal father automatically, by presumption, the moment they’re born. Children born to unmarried parents do not. Under the Illinois Parentage Act of 2015, an unmarried father is not a legal parent — with no standing to seek parenting time, no standing to seek decision-making authority, none of it — until parentage is formally established. Until that happens, the mother holds sole decision-making and parenting time by default, and the father has no schedule to enforce even if he is living in the home and providing day-to-day care.
There are three paths to establishing parentage: a Voluntary Acknowledgment of Parentage signed by both parents at or after birth, an administrative order through the state’s child support agency, or a court adjudication, which typically proceeds through genetic testing under the Act’s testing provisions. A man who believes himself to be a child’s father but whose paternity is contested or unacknowledged is also expected to register with the Illinois Putative Father Registry within 30 days of learning of the pregnancy or birth — a step that preserves notice and standing rights in later proceedings, including adoptions, but by itself establishes nothing. Registration is not parentage. Only a VAP, an administrative order, or a court adjudication is.
Only after one of those three has happened does an unmarried parent get access to the best-interest framework — the seventeen factors under 750 ILCS 5/602.7 that determine parenting time, and the parallel factors under 750 ILCS 5/602.5 that determine decision-making authority. Before that point, the analysis a court would apply to two married parents in a divorce simply does not attach. There is no interim best-interest hearing weighing caregiving history or emotional bonds for an unmarried father who hasn’t cleared the parentage threshold; there is only the mother’s default authority and the father’s task of establishing legal standing first.
The Comparison
Line the two frameworks up, and the asymmetry is precise, not impressionistic — but it’s an asymmetry between two kinds of threshold, not between having one and having none.
“For a jointly cared-for dog, the threshold is factual. For a jointly parented child, the threshold is legal.”
For a jointly cared-for dog, the threshold is factual. Two unmarried people can walk into court, and once shared caregiving is shown through evidence, the court can weigh right there — vet records, testimony, who walked it and when — a judge moves straight into the ten-factor list: who did the daily feeding, how bonded the animal is to each party, how disruptive a change would be. Ownership paperwork helps, but by statute it isn’t dispositive.
For a jointly parented child, the threshold is legal, and it isn’t symmetric between the two parents. An unmarried father cannot get in front of any best-interest analysis at all until he has independently established legal parentage — through a Voluntary Acknowledgment of Parentage the mother must also sign, a state administrative determination, or a contested court proceeding involving genetic testing. Until one of those concludes, Illinois law doesn’t weigh his caregiving history or his bond with the child and find it wanting; it doesn’t ask about it at all, because the proceeding where that evidence would matter hasn’t opened. Meanwhile, the mother’s legal status attached automatically at birth, and her decision-making and parenting-time authority is default and exclusive for as long as his remains unresolved.
Put plainly: Illinois will now ask “did you actually care for this animal” as the threshold question in a possession dispute over a dog. For a child of unmarried parents, the threshold question isn’t about caregiving at all — it’s “have you completed a separate legal process to become a parent in the eyes of the court” — and one parent is exempted from answering it by default.
This is not a claim that HB 4540 is bad policy, or that the Parentage Act’s testing and acknowledgment requirements are unjustified — DNA-based parentage confirmation exists for real reasons, including protecting children from disputed or fraudulent paternity claims, and the Act is itself gender-neutral on its face, extending “regardless of the legal relationship of the parents.” The comparison isn’t about whether either threshold is defensible in isolation. It’s about the kind of threshold each area of law chose: a factual showing of caregiving for animals, a formal legal proceeding for children, with one parent exempted from it by default. Run the test the other direction, and it still holds: a parent who has not established their own legal status relative to a child — through surrogacy, an unacknowledged birth, or otherwise — hits the identical wall, regardless of gender. But in the ordinary unmarried-birth case, it is the father who starts outside the door, because the mother’s status attaches automatically and his does not.
“Illinois will now ask ‘did you actually care for this animal’ as the threshold question in a possession dispute over a dog.”
Why the Kind of Gate Matters More Than the Factor List
“The proceeding where that evidence would matter hasn’t opened.”
It would be easy to focus on the ten well-being factors in HB 4540 and note how closely they resemble the seventeen best-interest factors in 750 ILCS 5/602.7 — caregiving history, emotional bonds, stability, routine, all present in both lists. That resemblance is real, but it’s not the story. Both frameworks gate their factor lists behind a threshold; the story is what kind of threshold each one chose.
“Both frameworks gate their factor lists behind a threshold; the story is what kind of threshold each one chose.”
For the animal, the gate is evidentiary. “Shared responsibility for care” is a fact a court can examine directly and immediately, through vet records, adoption paperwork, or testimony about who fed and walked the dog. Clearing the gate and having the well-being factors weighed can happen in the same proceeding, in front of the same judge, on the same day.
For the child, the gate is a legal status the unmarried father doesn’t yet hold, established through a separate track — VAP, administrative order, or court adjudication — that runs on its own timeline and, in contested cases, its own evidentiary standard entirely apart from caregiving. The Parentage Act’s stated purpose, giving children a clearly recognized parent-child relationship, is legitimate on its own terms. But it also means the well-being-centered inquiry that can now reach a jointly cared-for dog on the strength of a vet bill is, for a child of unmarried parents, gated behind a proceeding that doesn’t run on the same evidence, doesn’t move at the same speed, and doesn’t apply to both parents equally — because only one of them needed it to begin with.
Rosie’s Law closed a gap for pets by making the threshold factual. The gap it didn’t touch — because it wasn’t built to — is the one still sitting inside the parentage statute next door, where the threshold remains legal, and asymmetric.
“Rosie’s Law closed a gap for pets by making the threshold factual. The gap sitting inside the parentage statute remains legal — and asymmetric.”
Illinois’s House Bill 4540, the Companion Animal Custody Equity Act, is now Public Act 104-0613. It passed the Illinois House 72–38 on April 14, 2026, the Senate 52–7 on May 19, 2026, and was signed by Governor JB Pritzker on July 24, 2026, taking effect January 1, 2027; the enrolled bill text, vote history, and Public Act status were pulled directly from the Illinois General Assembly’s bill-status system, which shows the law amending 735 ILCS 5/19-101 and adding new Sections 19-106.5 and 19-130 to the Code of Civil Procedure’s replevin article. The Animal Legal Defense Fund’s analysis of the law, published shortly after passage, provided additional context on its legislative origins and its relationship to Illinois’s earlier, marriage-only pet custody statute. The best-interest factors governing parenting time in Illinois are set out at 750 ILCS 5/602.7, and the parallel factors governing significant decision-making responsibility are set out at 750 ILCS 5/602.5, both part of the Illinois Marriage and Dissolution of Marriage Act and confirmed against the Illinois General Assembly’s official statute text. The framework for establishing legal parentage in Illinois — voluntary acknowledgment, administrative determination, or court adjudication through genetic testing — comes from the Illinois Parentage Act of 2015, codified at 750 ILCS 46/, which states its gender-neutral intent at Section 102; the putative father registry provisions are found at 750 ILCS 50/12.1.
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