If you want a ban, plant here.

The ladder is only one in spawnroom. It is hidden from player leaving and it stops player leaving, you will be banned if he cant leave, Killing incoming players is fine. But remember they might spawn in that area too. So plant carefully.
Rule: You may boobytrap objectives. However prevent player from leaving spawnroom in any way, including death by secret lam and you will be banned.
That includes planting outside the spwnroom, if it prevents the player leaving the spawnroom...