Nobody Knows What a Robot Is

Regulate autonomy, not anatomy.

This week’s robotics post is co-authored by Emerson Alden and Amelia Michael, research fellows on the AI team at the Foundation for American Innovation. It was produced as part of FAI’s Physical Intelligence Project, and accompanies the Robotics Classification Framework available here.

It is important to get robot definitions right when crafting legislation. Fuzzy definitions can lead to overinclusion (e.g., accidentally regulating robot vacuums when trying to legislate warehousing robots) or underinclusion (e.g., accidentally exempting robots with comparable vulnerabilities to humanoids because they move on wheels rather than legs.)

In November of last year, Senators Cassidy and Coons introduced the Humanoid ROBOT Act of 2025. The intent of this bill is “To reduce the risk to the national security of the United States posed by humanoid robots produced in certain countries.” To avoid unintentionally including other types of robots—such as robot vacuums, self-driving cars, or fixed-based industrial arms—they are careful to define what counts as a humanoid. According to their bill, a “humanoid” is a robot which “possesses a body structure that simulates the human form, including a head, torso, arms, and legs, or any configuration that resembles a human silhouette.”

This presents immediate ambiguity: over the last year, two-armed wheeled mobile manipulators (sometimes referred to as “mermaids”) have grown in popularity—see Dexmate’s Vega, Sunday’s Memo, AGIBOT’s G2, and Unitree’s G1-D. Does this form factor “resemble a human silhouette”? That would be left for the courts to determine. But such robots have the same potential for data exfiltration, remote access, or other security vulnerabilities as any bipedal humanoid.

Similar challenges appear in other proposed robotics legislation. Take the recently proposed GUARD Act of 2026, which directs the Intelligence Community to assess whether to place certain humanoids and quadrupeds on the Federal Communications Commission’s Covered List. It defines humans and quadrupeds as robots that use “2 or 4 articulated limbs for locomotion, navigation, or movement on the ground.” This would explicitly exclude mermaids and six-legged hexapods.

The definition problem is not exclusive to legislators. ISO 8373:2021 contains little guidance for assessing a robot’s level of autonomy, saying, “For a particular application, degree of autonomy can be evaluated according to the quality of decision-making and independence from human [sic].” Without such guidance, legislators are left to use form factor as a proxy for autonomy.

A great variety of robot form factors already exist, and the boundaries among them are often blurry (for example, Collaborative Robots’s Proxie could be considered an autonomous mobile robot, a cobot, or even a humanoid). It is also likely that more form factors will emerge as robot autonomy improves. If legislators define the scope of regulation according to the form factors that exist today while attempting to address challenges presented by higher levels of autonomy, many bills will come with a short countdown to obsolescence.

To help address this issue, we’ve come up with a detailed classification for robots, complete with a list of legislative definitions that legislators can slot into bills. We hope that this will be a helpful resource for policymakers attempting to navigate the increasingly significant field of robotics.

Read the full classification framework and legislative definitions here.