California, for example..has water right laws. It became legal only in 2012 to collect roof top rainwater. Using said water for landscaping requires a permit.
"A water right is legal permission to use a reasonable amount of water for a beneficial purpose such as swimming, fishing, farming or industry"
"Water is protected for the use and benefit of all Californians. California's waters cannot be owned by individuals, groups, businesses, or governmental agencies. But permits, licenses, and registrations give individuals and others the right to beneficially use reasonable amounts of water."
Thus this makes it illegal to use/collect/harvest water beyond whatever fee permitted usage allows.
Although some farm land has grandfathered riparian water rights.
Yes, breaking a law is illegal. But water collection in CA is regulated, not prohibited. There is a difference, as much as you might not want to see it.
I definitely fall in the middle here. It's absurd to prevent people from collecting some water. It's just as absurd to let people collect as much as they can.
