The collection of rainwater is illegal (against the legislation... the will of those who govern) only where freedom is illegal.
Start collecting your own rainwater and you might no longer need the public water supply.
Start recycling your water (using grey water from sinks and things other than toilets) and you might be able to irrigate gardens and orchards at little to no costs... letting you grow your own food without the public water supply.
That there is obstructing interstate commerce where I come from. If people started growing their own (non gmo, non-pesticide ridden) foods they would be skipping sales tax, avoiding medical bills, living longer (costing the SS program more!), paying less to local governments, and more. Talk about outlaws! evil grin
What if people started using humanure and using that to enrich the soil (and avoid sewer costs!) and grow even more food? While animal manure might be good for the soil us humans are not animals... so don't even think about it.
No way.
Just say no to rain water collection, grey water collection, composting, growing food, self-sustainability, and other subversive activities.
(oh say can you see...)
Do your duty as a good citizen, head to your nearest chain grocery store, buy some great food (preferably something either classified as a pesticide or lacking any nutritional value whatsoever), get all manner of diseases (support the sickness industry), and die young (don't leech off of social security).
Do your civic duty and be a good submitizen.
Stop even thinking about getting your own water. That might lead to other nefarious plans that would entirely change how things work.
Oh yeah, and report any rain water thieves you come across.