Summoning does not work exactly like the Monster Summoning spells.... There is a fundamental difference. Creatures in the realm spell are transported from one place in the Prime Material to another and after the spell ends, they don't teleport back, but they stay to pillage the place...

This brings some questions

1) Can you Dispel the Summoning? What exactly is dispelled? The control (and the ogres start to pillage the province)? The summon itself (and the ogres are teleported back home)?

2) Can you dispel a Monster Summoning spell?

In other words... the existence of the ogres in the province, AFTER they have been summoned, is depended on magic and therefore can be dispelled? The control of the caster is depended on magic and therefore can be dispelled?

Any input/insight is most welcome