Some homeowners upset at the sight of weeds in their yard, argue "it's my yard and I have the right to put herbicides on my lawn if I want to." Make an argument against this point of view and for laws prohibiting the use of such herbicides.
This is, essentially, an issue of property rights and where a person's right to do as they wish with their property ends.
An argument against this point of view would stress that our right to act as we wish generally ends when we start to hurt other people. We have a right to speak freely, but not in such a way that our speech wakes people up in the middle of the night. We have the right to wave our arms, but not if that arm-waving ends up hitting someone in the face. In just such a way, we do not necessarily have the right to put whatever we want on our lawn.
The chemicals we put on our lawn can become urban runoff and contaminate waterways. This harms people other than ourselves. For this reason, we can argue that we have no right to put herbicides on our lawn since they will end up becoming pollution and harming others.