I'm GMing for a group of high level PC's who just came up against an equally high level cleric. The cleric cast antilife shell, and the party wizard's answer was to summon a monster within the shell's 10ft radius.
The spell reads that it "hedges out" creatures within the radius, so that's what I had it do. (Note: The PC didn't summon an outsider, elemental, or undead creature. It was a Dire Tiger.)
I suppose an argument could be made that the creature popping up that close to the gentleman cleric would make the shell pop, but that seems like too much of an exploit. To me, the spirit of the spell is that it cannot be used offensively, and letting someone negate the spell with a level one summon would be cheese and crackers.
Thoughts?
Since a creature brought via "Summon Monster X" can't be summoned into an environment that can't support it, and the shell "prevents the entrance of <specified creatures>", I'd say the wizard would have to choose an area outside the shell to summon the creature into.