The feat is available by the same rules as ever. (i.e. must be able to cast 3rd level spells)
The change is that at level 14 (the start of 4th level spells for Rangers), there's a check, and if a Ranger has Eschew I, that ranger can cast 4th level spells without components.
This is a special allowance for Rangers being made in the Eschew logic.
