There is an edition with modern spelling. It's outrageously expensive, though:
http://www.amazon.com/Richard-Hooker-Laws-Ecclesiastical-Polity/dp/0199604959
But here's the thing: after I read it, I decided it wasn't as good as simply reading Hooker's original instead. You should try it. Best of all, it's totally free on Google Books. Don't be put off by the fact that it's late c.16 theology. It's still Early Modern English and you should be able to read it.