From Doomsday Wiki
From the game
Syntax: ADVISE <player> MP: 4 The advise command is used as a quick way to determine if it is safe to launch an attack on the given player (safe meaning they are within your level or jurisdiction and no penalty will be given.)
The advise command is a good way to check if you are allowed to attack someone. It is not only linked to whether someone is too small or not but whether or not you can legally retaliate against someone small who made the mistake of attacking you.