I can't imagine that there were laws or decrees, as the development of the language, insofar as they merged (along with other influences, such as the Old Norse language) into a language that we would recognise as Modern English, resulted in many various dialects. Personally, I study Middle English literature, and Middle English is recognisable as the 'next step on' from Old English (ie. Anglo-Saxon). The reason why I say that it's unlikely there were regulatory laws is that Middle English texts are extremely dialectical, to the point that scholars are often able to identify where an author or a scribe likely came from looking at the nuances of spelling and the words/forms of words they use. For example, Chaucer, who wrote from about 1370, wrote in the [London dialect of Middle English] (http://writersinspire.org/content/geoffrey-chaucer-father-modern-english). Indeed, in one of The Canterbury Tales ('The Reeves Tale'), he 'mocks' some of the characters by writing their speech in a northern country dialect, which would have appeared uncultured and crude to his metropolitan audience (For the specifics of this episode, see p. 850 of The Riverside Chaucer, ed. Christopher Cannon, 2008.)

I realise that the Chaucer example might be a bit late to answer your question completely, but I'm just using as an example to demonstrate that the development of Middle English was very non-standardised. It was heavily dialectical from region to region. I'm not a philologist (a philologist would have been able to answer your question much more comprehensively!), but even from just studying texts from a literary interest, you realise how Middle English was a real patchwork of influences. If you're really interested in this stuff, I'd recommend reading Sir Gawain and the Green Knight, which is an excellent poem in its own right, but philologically it's fascinating. I especially recommend [this edition] (http://www.amazon.co.uk/Gawain-Green-Knight-Norman-Davis/dp/0198114869/ref=sr_1_2?ie=UTF8&qid=1393592345&sr=8-2&keywords=sir+gawain+and+the+green+knight+tolkien), because it has a very good glossary, explains a great deal about the dialect (which is a more northern dialect of Middle English), and details the etymological roots of words, so you can see which ones derive from Anglo-Saxon, Old Norse, Old French etc.