If none of the matching code groups CG1, CG2, CG3 … contain the EX exclusive flag the PA allow permission sets are combined.
PA = PA1 + PA2 + PA3 + …
If exactly one code group has the exclusive flag –say CG1— then only that code group applies and PA=PA1.
It is considered an error for more than one code group that matches a given assembly to have the exclusive flag. Should this occur and exception is thrown and the code is not loaded.