Medieval 2 contains several new hidden resources. 2 of them are: no_brigands and no_pirates.

You can see an example of their use in the descr_regions.txt file:

Code:
North_America
	Miccosukee
	aztecs
	Native_Rebels
	212 198 206
	tobacco, coal, america, no_pirates, no_brigands
	5
	6
	religions { catholic 0 orthodox 0 islam 0 pagan 100 heretic 0 }
The provinces these resources are placed in will not spawn pirates off their coasts or brigand slave armies on land. They can thus be used to keep an area desolate or untouched - such as the Americas in M2 - or if you are a more adventurous modder then the brigands in this area might represent a different type of enemy that will only appear after a particular time or event (perhaps conquering a significant settlement).

You can then reactivate brigands and pirates with the following in your campaign script:

Code:
                add_events
					event	counter	disable_no_brigands
        			date	0
					event	counter	disable_no_pirates
        			date	0
       			end_add_events
Try enable_no_brigands as well - haven't tested it yet but maybe it will work.