Is there a way for an outsider to protect itself from being called by a planar binding spell?
Is there a way to bolster its resistance to being called?
I would say dimensional anchor would would prevent anyone from calling you at all , since it would stop any kind of planar travel: ("completely blocks extradimensional travel.").
Anything which boosts its will save or spell resistance? Plus yes, dimensional anchor.
Normally when using the Calling spells you get a generic (aka random) member of the group yu are calling.
To get a specific individual you need their name. Their true name, not a "people know me as ... Tim" one. That is one of the reasons why Outsiders guard their True Names so thouroughly.
Dont let your true name get out there, then you cant be called by bothersome mortals directly.
Normally when using the Calling spells you get a generic (aka random) member of the group yu are calling.
To get a specific individual you need their name. Their true name, not a "people know me as ... Tim" one. That is one of the reasons why Outsiders guard their True Names so thouroughly.
Dont let your true name get out there, then you cant be called by bothersome mortals directly.
Trust me, i have dealt with people before who say that "No matter how obscure you are, if you are an outsider your truename can be found in a book somewhere with a Knowledge Planes check even if you haven't recorded or told it to anyone because thats what the book says" and yes, this person was going to use it on the Aasimars and Tieflings in the party. So don't underestimate the rediculousness of people.
I'd go with the simple and easy method of outsiders aren't stupid and would have themselves specifically warded against being called specifically unless they wanted to be called.
Otherwise calling generates a generic outsider of the appropriate type, which should probably be sufficient. But if you want a specific one your going to have to work a bit harder for it.
As for calling native outsiders (Tiefling and Aasimar) they would first need to be on another plane from the caster.
Other Outsiders
While the groups above detail all the major types of outsiders, the Great Beyond is called great for a reason, and there are countless other outsiders that a potential binder can call. In theory, any outsider can be called and a binder can attempt to press that creature into service, though the proper strategy for doing so is contingent on the abilities, desires, and goals of the particular outsider.
There is one group of outsiders that it is more difficult to bind: the native outsider. A native outsider cannot be called and bound from the Material Plane. In order to call any outsider, it must be on a different plane from the binder. Native outsiders (or other outsiders currently manifesting on the Material Plane) can only be called and bound by spellcasters on a different plane.
I like the "on separate planes clause". Although that one would be so easy to overlook.
Another one I just thought of is class levels which translates to more hit dice. Outsiders with more than 18 hit dice seem to be uncallable.
Thanks everybody.
The on separate planes clause can be got around as simply as a plane shift, which can be obtained via lesser planar binding/ally from a nightmare or janni if you have no other access. i.e. if you're able to call creatures at all, you can get around the clause.
This thread reminds me that the text for the Ultrodaemon in the 1st Edition AD&D Monster Manual II mentioned that some Ultrodaemons got their arts of summoning (AD&D didn't have separate Summoning and Calling back then) to such a level that they could even summon mortals from the Material Plane. Unfortunately, this seems never to have been fleshed out or otherwise followed up.