  We establish a set of general results to study how the Galois action on
modular tensor categories interacts with fusion subcategories. This includes a
characterization of fusion subcategories of modular tensor categories which are
closed under the Galois action, and a classifcation of modular tensor
categories which factor as a product of pointed and transitive categories in
terms of pseudoinvertible objects. As an application, we classify modular
tensor categories with two Galois orbits of simple objects and a nontrivial
grading group.
