Why can't you play it? it should work just fine. All the missions, patrols, strikes, Crucible maps and public events that you had access to last month should still be there. All your equipment should still be there. Do you mean that you can't do any of the new content? The stuff in TTK, the game that you can't currently afford? Why does that surprise you? What made you think new content (including an increased level cap) would be available to you without buying the new expansion? Yes, this is legal. Bungie hasn't done anything remotely illegal here. They haven't taken any content from you (although you no longer qualify for some activities). In fact, over the last year they've given you quite a bit of new content for free.