Ok, I tested this on Wowlord server (wowmolly) And, well, I found out how a pally can DW without the ability!
Ok, first, equip any two-hander.
Then, get a sword that is Off-handed.
From your inventory, right click the off-handed sword.
It will go on your offhand!
Now, equip a mainhand sword, and you are a Dual-wielding pally!