then discard a Land battle card to remove a Hoplite adjacent to Laconia.
It doesnt actually specify which one (friend or foe) the second clause. Thematically I think it's meant to be a Spartan hoplite, but the card is not clear
Actually, you can remove anyone you want. But normally it would be an Athenian or Delian League. It is not supposed to be a penalty, but an extra benefit. So the second part is not required.
Unlike most Greek cities, Sparta didn't have walls. When an enemy came with hostile intent to Spartan territory, the Spartans marched out to defeat them. The title of the card comes from a famous incident of a visiting dignitary who asked where Sparta's Walls were. The Spartan leader pointed to some nearby soldiers and said, "These are Sparta's walls", I assume followed up with a noisy but precise ancient version of "Order Arms".