As state attorneys general aim to play a more active role in U.S. merger enforcement, several state legislatures have introduced so-called “mini-” or “baby-” HSR legislation proposing new merger filing requirements. Driven by the model Uniform Antitrust Premerger Notification Act (UAPNA) released last year, these statutes focus on requiring earlier and mandatory submission of federal HSR filings to state-level enforcers. As implementation of the model law may vary, some states are introducing broader requirements to require reporting of additional deals in health care or other target sectors. With the first regime due to take effect in Washington State on July 27, 2025, and similar pending in several other states, this development is set to drive some sleepless nights for dealmakers.

What can you expect when you’re expecting (“baby HSRs”)?

The Uniform Law Commission, an organization of legal professionals who propose uniform and model state laws, introduced UAPNA on July 24, 2024. Previously, state AGs lacked direct access to HSR filings, having to obtain party waivers to receive filings from the FTC or DOJ, or else obtain merger evidence through cumbersome subpoenas. UAPNA facilitates AGs’ merger enforcement efforts by compelling simultaneous notification and granting AGs access to HSR forms and related materials without the need for more resource-intensive measures. 

On April 4, 2025, Washington became the first state to enact UAPNA. Set to take effect on July 27, 2025, this new legislation requires that merging parties filing under the HSR Act submit a simultaneous filing to the Washington Attorney General if their transaction meets the relevant local thresholds. 

Although Washington is the first state to enact UAPNA, it is unlikely to be the last. In recent months, Nevada, Colorado, California, Utah, West Virginia, Hawaii, and the District of Columbia have introduced parallel bills modelled after UAPNA in their legislatures. This dovetails with an increasingly aggressive enforcement posture states have pursued in concert with federal authorities and on their own accord. Transacting parties can expect a focused review of local markets and the possibility of additional investigatory and enforcement hurdles as legislation continues to grow.

What deals are captured?

UAPNA applies to: 

• Parties whose principal place of business is in the enacting state; or 
• Parties whose net sales in the enacting state of goods or services involved in the transaction is at least 20% of the federal HSR filing threshold 

States have discretion to cast a broader net in implementing UAPNA. For example, Washington’s statute as implemented also requires all healthcare providers and provider organizations conducting business in Washington to file.  

What is the process?

Notably, UAPNA as implemented to date does not have suspensory effect or introduce any additional waiting period. Instead, filing parties remain subject to the 30-day waiting period required under the HSR Act. However, the statutes will add complexity to filings and create new exposure for deals that fail to file in a growing number of states. 

Under UAPNA, parties must submit a contemporaneous copy of their HSR filing to the enacting state’s AG. Parties with a principal place of business in the state are also required to submit attachments to the HSR form, while parties satisfying just the net sales threshold need only provide such attachments within seven days of receiving a request from the state AG. Like parties meeting the 20% net sales threshold under UAPNA, healthcare providers and provider organizations must submit HSR form attachments within seven days if requested by the state AG. Below are notable aspects of UAPNA contrasted with existing requirements under the HSR Act: 

How far-reaching will the changes be?

Other states are pursuing targeted approaches to counter perceived gaps in federal merger enforcement by requiring filings for additional deals within particular sectors that are not reportable at the federal level. Such "gap-filling" efforts include existing legislation focused on regulating specific industries, such as healthcare or retail providers. Indeed, California and at least 13 states have imposed a healthcare specific pre-notification law variously requiring filings with states’ attorneys general and/or healthcare policy agencies. 

Similarly, California requires retail grocery and retail drug firms engaging in acquisitions to notify the state AG 180 days before closing if the acquiring party has filed an HSR notice or is acquiring more than 20 retail drug firms or retail grocery firms. This regulation represents a broader effort to address market consolidation in critical local industries with strong consumer implications.

Some states are also expanding merger enforcement through broader legislation and policy changes targeted as substantive enforcement standards. After several broad iterations that did not make it through the state legislature, New York has introduced a new antitrust modernization bill in January 2025 that reintroduces a new obligation for firms to submit HSR filings to state enforcers wherever the parties are “doing business” in New York. Also in January 2025, the California Law Revision Commission recommended updating the state’s premerger notification rules and expanding enforcement powers. The proposed changes would allow the state to challenge mergers presenting an "appreciable risk of harm"—a lower standard than the Clayton Act’s “substantially lessen competition” standard.

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