Splash contests are classified as games of skill, not gambling. Availability depends on your physical location at the time of entry.
Real-money, public contests: Available in 30+ states. Check the state availability map for your state.
Private (self-managed) contests: Available in all 50 states, Canada, and other countries — no restrictions.
Note: You can live in a restricted state and still play — you just need to be physically located in an eligible state when you enter a contest. After entering, you can make picks from anywhere.