Freedom means different things to different people. But one way of understanding what it means to live in a free country is that you don’t have to worry about the government taking action against you for no good reason.
What is a good reason? One possibility is that you have not broken the law. But in the US, this is no longer an adequate reason. There are so many laws that people probably break them daily. Thus, if the government wants to get you for some other reason, they can arrest and prosecute you for breaking one of the laws that everyone breaks. This is obviously a strong reason for cutting back on the scope and number of our laws.
But under the existing system, your freedom and protection turns on the discretion and judgement of prosecutors, police officers, and other government officials. Thus, if one pisses them off – if they get mad at you for a good or bad reason – one is in danger of being prosecuted. This suggests that our system requires a mechanism for constraining discretion.