There are a lot of illegal things that happen on the Internet. Innocent people are even hurt or killed because of the things that happen in the dark corners of the Internet. For this reason, there is nothing wrong with law enforcement wanting to step in and regulate. It is for public safety.
The dark net probably needs more regulation than any other part of the internet. However, I guess it could be argued that it can't be regulated because that is where all the criminal and not so nice activities are happening on line. I'm sure those who use it can dodge any thing put in place to try to stop it.
The darknets which constitute the dark web include small, friend-to-friend peer-to-peer networks, as well as large, popular networks like Freenet, I2P, and Tor, operated by public organizations and individuals. Users of the dark web refer to the regular web as Clearnet due to its unencrypted nature. Although much of the dark web is innocuous, some prosecutors and government agencies, among others, are concerned that it is a haven for criminal activity.
First, it would be rather hard to regulate. The FBI has tried, and succeeded in some cases, but the darknet as a whole is such a vague concept: You have the illegal stuff, which most people think of when they think darknet. Anonymity too. Take for example, the SecureDrop concept. It was a way for whistleblowers and such to leak information to journalists, and a large part of why it worked was the darknet. Think Edward Snowden: He didn't necessarily use the darknet, but if he did you had better believe the NSA, CIA, FBI, and other such DC three-letter alphabet soup would jump on any chance of shutting him up. There are some rather seedy parts of the darknet, where you can get anything, hitmen even. But there are also other aspects. And the darknet is a vast thing, spanning more than a couple sites. It is part of the regular, regulable Internet, and a good chunk of it, but that doesn't mean it's easy to find.
The dark net is a place of freedom. While it has its unsavory side there are good things about its anonymity as well. People from oppressive regimes can speak their mind without being caught. Its a place where people who can't otherwise can buy things they may need and help get the message out about what really goes on in their government.