use whatever style fits your paper. grammar rules are for general use; if you know them and the reasons behind them, you ought to be able to safely break them and avoid ambiguity in your writing.
"however" typically functions as a conjunctive adverb, along with thus, therefore, nevertheless, etc. if you're going to be a grammar nazi, "however" should be used only immediately after a semicolon (e.g., "I generally hate snot-nosed pricks; however, that snot-nosed prick is particularly annoying."), or in a more substantive adverbial sense:
But much you may think that's true, you kind of have to admit that using 'however' at the beginning of this sentence would have made a lot more sense.
--lastly, i wouldn't trust court opinions about grammar. most of them are grammatically inept (however
conceptually rich or bereft they may be).