Players can still play lands from graveyards if an effect allows them to. Similarly, effects can put land cards onto the battlefield from any zone.

If an effect exiles a card from a graveyard or library and allows a player to cast it, the player may do so. The spell is cast from exile.

Look at the card as it exists in your graveyard or library to determine whether it can enter the battlefield. If it’s a double-faced card, use its front-face characteristics only.