Is it illegal to do a lottery in WoW?

MY sister and i did a lottery the last few days, where we wrote "win" or "loss" on plain letters and put them in the auction house and advertise "Lottery buy a plain letter winner gets blah blah", is this illegal? We're only making like 500-1k(400g goes to winner, and my sis and i split it up) this is small potatoes because i have 3 80s but its just a fun thing to do. We also made a guild, its a leveling guild but the guild will set up lottery s for fun, would the guildies get in trouble for participating in the lottery? thx!