EX Hooligan Combination is a very, very risky move to use, as it makes Cammy extremely punishable. This isn't very easy to spam because it consumes meter (1 bar), and you obviously need a Super meter with some bars to use it.
To punish it, there are several options. One, is crouch. If you crouch, the EX Hooligan will simply jump over your character on the other side, not even hitting you. Another option similar to crouching is to forward dash when Cammy begins the inital jump. This will actually ruin the trajectory and cause her to land behind you. However, DO NOT backdash. Cammy will grab you even if you backdash, so forward dash to avoid the throw.
Another very easy way to punish is to spam cr.lp (crouching, light punch). Most characters can easily combo from cr.lp into other moves.
If your character has anti-airs, use them. During Hooligan Throw, Cammy is considered airborne, so use anti-air moves, including DPs (shoryuken), abel's FS (falling sky), El Fuerte's Guacamole, etc.
One last thing to note. EX Hooligan should be typically used to punish fireballs. This means if you face a player who repeatedly spams the move, don't try to Hadouken them out of it or fireball constantly, or risk getting punished.