The word you’re looking for is usually “wonk” or “policy wonk.”

Quick definition

People who get deeply into the nitty‑gritty of a subject like government rules, legislation, or regulations are often called:

  • Policy wonks – people who love the fine print of policy design and implementation, often more than the politics or drama around it.
  • Technocrats – experts focused on technical details and data when making or advising on decisions, especially in government or big institutions.
  • People with an obsessive attention to detail – sometimes praised as meticulous, sometimes criticized as nitpicky, depending on context.

In casual conversation, “policy wonk” is the most common, neutral, and even slightly affectionate term.