ESIGN (Electronic Signatures in Global and National Commerce Act, 2000) is the US federal law that established the legal validity of electronic signatures and records in interstate and foreign commerce. UETA (Uniform Electronic Transactions Act, 1999) is a state-level model law adopted by 49 states plus the District of Columbia (New York adopted similar but distinct language).
Both laws share the same core principle: an electronic signature has the same legal effect as a handwritten signature when (1) the parties consented to do business electronically, (2) the signer can be identified, (3) intent to sign is captured, and (4) the record is retained and reproducible.
For most B2B SaaS, marketplace, and consumer contracts, ESIGN/UETA-compliant signatures are sufficient and don't require additional certification.