The issue here is that you are outsourcing police work to ill motivated, poorly and sloppily trained, not monitored and obviously biased
It also is a great way of masking austerity and cuts by getting normal people to do police work. It sets a really bad precedent, if you can issue fines, why not other police work like getting people to investigate each others crimes? Normal people are not police, just like they are not judges (police or people).
There have already been cases of reliability of these laser guns when used by properly trained people, and now we want to get someone who’ll store it in their living room? How can you ensure that the fines are accurate and proportionate, especially in a system where arguing against a laser is extremely difficult.
Beyond this I do not want to live in a society where you turn one person against the next, with legal ramification. As BL says, this is not someone acting out of public safety, it’s someone who gets a kick off authority…