The specific federal law that requires lease terms to be disclosed, and what it actually guarantees.
The Consumer Leasing Act (CLA), implemented through the Federal Reserve's Regulation M, requires lessors to disclose specific figures before you sign a personal-use lease over a set term: the gross capitalized cost, any capitalized cost reduction, the adjusted (net) cap cost, the residual value, the rent charge, and the total of payments. This is the legal basis for the disclosure box you'll find in any compliant lease contract — and the reason the "three numbers" checklist elsewhere on this site (money factor, residual, total of payments) is always obtainable, even if a salesperson is reluctant to state it out loud.
Reg M requires disclosure, not favorable terms — it doesn't cap the money factor, doesn't require a cooling-off period, and doesn't limit early termination charges. There is no federal "right to cancel" a lease within a few days the way there is for certain door-to-door sales under the FTC's separate Cooling-Off Rule; a small number of states add their own lease-specific protections, so check your state attorney general's consumer protection page for anything beyond the federal floor.
A CLA/Reg M violation can be reported to the Consumer Financial Protection Bureau (consumerfinance.gov) or the Federal Trade Commission (reportfraud.ftc.gov). Keep the signed disclosure document — it's the primary evidence in any dispute about what was actually promised versus what was delivered.