What the technical rules govern
The FIA Technical Regulations run to hundreds of pages defining every dimension: bodywork boxes, wing sizes, floor geometry, minimum weight (768 kg from 2026), power-unit architecture, fuel-flow limits, crash-test requirements. Cars are measured, weighed and inspected ('scrutineering') throughout every weekend.
The rules exist in tension with themselves: tight enough to keep costs and speeds sane, loose enough that clever engineering is rewarded. That gap is where championships are won.
The loophole hall of fame
F1's history is a museum of legal-until-banned inventions: Brabham's 1978 'fan car' (won its only race), the 2009 double diffuser (won Brawn both titles), the 2010 F-duct, the 2020 Mercedes DAS steering system. Each exploited wording, not intent — and each was outlawed only after proving devastating.
The modern process is more collaborative: teams query the FIA before building ('is this legal?'), and technical directives clarify gray areas mid-season. But the treasure hunt never stops.
Enforcement
Legality checks include template measurements, deflection tests (bodywork must not flex beyond limits), weighbridge checks, fuel analysis, and the plank — a wooden skid block whose excessive wear proves a car ran illegally low. Disqualifications happen: Hamilton and Leclerc were both excluded from Austin 2023 for plank wear.
Post-race, any car can be torn down for inspection. Championship-deciding technical protests are rare but seismic when they land.