I'd ban people who want to ban cats.
Those herds of sheep and deer might become a little problematic over time as their population grows. I'd reintroduce wolves, elk, bears, and lynx, along with fully supporting a fuller reintroduction and protection for Beaver and Otters.
Naturally, systemic pesticides would be out the door so that bees and insects have a chance to exist, I'd subsidise organic production and traditional mixed farming with encouragement for reinstating proper hedgerows, drystone walling, heavily encourage the use of horses over cars (thus also providing significant free and readily available fertiliser) and anybody proposing we expand into other worlds is made to sit in a darkened room and work out how to fix the mess we've made of this world before we're ever allowed to go and bugger up somewhere else.
Every home would have to have a decently sized sink and garden space, along with enough room to get a sofa or bed in through the front door. All washing and cleaning products would be environmentally safe, as would all cosmetics.
Oh, and unless it's for medical purposes, plastic will be banned. That way, you do get your injections, your removable casts and braces and suchlike, but you do not get your manky bags, plastic hairclips or googly head ornaments.