I think the "Zero Tolerance" comparison is very apt. Here's a little wiki excerpt on the subject that seems especially interesting in light of TDKR:
According to scholars, zero tolerance is the concept of giving carte blanche to the police for the inflexible repression of minor offenses, homeless people and the disorders associated with them. A well known criticism to this approach is that it redefines social problems in terms of security, it considers the poor as criminals, and it reduces crimes to only "street crimes", those committed by lower social classes, excluding white-collar crimes.
I definitely think TDKR was going for some of that "police state" vibe, where the new policies have helped clean the city but are also very repressive.
As far as the Patriot Act allusion, TDK certainly had "surveillance" themes going on with the sonar machine, which was even stated to be a government project. So the series had already established a light sci-fi setting wherein there are more advanced surveillance techniques in existence, as well as the themes associated with it. It's definitely become a common theme for Jonah Nolan too, considering the entire premise for his show Person of Interest
is based around the idea. It's not essential to consider in relation to the Dent Act, but it makes sense and is good food for thought.