This is a point of irritation for me, at what point does an individual cease to be responsible for their actions? Providing that they are not under the influence of something, of course. Why should it be the responsiblity of the heathcare provider to make sure these SI patients are protected from themselves?
In PA we have what is called a "302" (a 5150 in CA) basically an involuntary admission BUT you have to have a petitioner in order to carry out this order.
This is the sticky part, the state police will seldom agree to petition, and then we have to go through the process of finding a petitioner. Our Crisis team usually evaluates this person and then decides if they are indeed suicidal (most arent). we see a lot of "no harm contracts" signed, and, after roughly 6-8 hours the person has eaten, received lots of attention, sobered up and they go on their way.