In short, it varies. The main factor to consider is your insurance. Some policies do allow hosts to provide alcohol to guests, while some explicitly forbid it. In these cases, if you did provide the guests with alcohol and an incident occurred, your insurance may not cover it. Always check to be sure.  If your insurance does allow it, providing a local wine or craft beer is an awesome touch. If not, a guide to local vineyards or breweries shows guests that you care about them having a great time.