US SMS compliance in 2026 sits on four overlapping pillars: the TCPA (federal statute), 10DLC (carrier registration), CTIA messaging principles (industry self-regulation), and direct carrier filtering rules from AT&T, T-Mobile, and Verizon. Miss any one and your messages get blocked, your traffic gets fined, or both. TCPA case filings alone hit 2,788 in 2024, up 67% year over year (Corporate Compliance Insights, 2025).