The Military Police Brigade is the most prestigious military sector due to their work, which allows citizens to live safely within the inner Wall and access to abundant resources. Therefore, it has higher authority over other military sectors. However, in reality, it is the most corrupted military sector due to a lack of oversight compared to the other sectors of the military. Due to their misuse and abuse of power, the Military Police Brigade is also at odds with the Garrison and especially with the Survey Corps. Only the top ten alumni from trainee squads can apply for the Military Police Brigade. However, according to the conversation between Hitch Dreyse and Boris Feulner, there are other ways to get in the sector such as fraternization, favoritism, etc.
Military Police Brigade source notes: The Military Police Brigade is the most prestigious military sector due to their work, which allows citizens to live safely within the inner Wall and access to abundant resources. Therefore, it has higher authority over other military sectors. However, in reality, it is the most corrupted military sector due to a lack of oversight compared to the other sectors of the military. Due to their misuse and abuse of power, the Military Police Brigade is also at odds with the Garrison and especially with the Survey Corps. Only the top ten alumni from trainee squads can apply for the Military Police Brigade. However, according to the conversation between Hitch Dreyse and Boris Feulner, there are other ways to get in the sector such as fraternization, favoritism, etc.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.