How is the law involved in contol of water pollution?

The law is involved in water pollution the same way the law is involved in speeding cars in traffic because those who pollute the water can afford the cost of a fine or penalty just as those who drive too fast in their cars can afford the cost of a ticket.

The "law" is in every person and it is every person's ability to create awareness at their own level and increase that awareness of water pollution to as many people around the person who is the polluter so as to cause due embarrassment enough to embarrass the law enforcement agencies and/or the polluter themselves to curb or cease their polluting ways.

Waiting for someone else and/or "the law" to get involved in control of water pollution is not the answer.

You are the answer.