The Federal government has the power to apply consent decrees to specific police departments when those departments are found to have used force excessively, per the 1994 Violent Crime and Law Enforcement Act[0]. This essentially opens police departments up to lawsuits if they exhibit a pattern of bad behavior. In fact, this law explicitly requires DOJ to issue an annual report on "the use of excessive force by law enforcement officers", although they haven’t.
> The fact that voters fail to hold their lower-level governments to account does not mean that all power (and failure) should be centralized.
The legislature and the executive derive their powers from the constitution, not legislation. This is demonstrated by the abundance of unconstitutional legislation.
Just wanna to add that Trump's DOJ isn't pursuing consent decree. In fact, the consent decree in Chicago was nearly finalized when Trump took office, and Sessions dropped it.
So they have the power to do it, but they definitely have the power not to do it at all.
> The fact that voters fail to hold their lower-level governments to account does not mean that all power (and failure) should be centralized.
0: https://en.m.wikipedia.org/wiki/Violent_Crime_Control_and_La...