In a recent game, the trading bug that causes the game to crash forced me to restart. Normal bug, so I figured, no big deal, I'll just embargo them.
It seems the embargo button only works if you're actually trading with the player. At the time, the player had no trade routes with me. Couldn't it be set up to be pre-emptive as well? I ended up having to buy a starport, a ship, and go to war just to continue my game.