Rabbinic ordination to students

Question

I was wondering,

What gives a rabbi the power to ordinate another rabbi? Can any Rabbi give smicha?

Answer 1

"Real" semicha -- involving the unbroken chain -- ceased long ago; the prerequisite there was having it yourself (in a chain that eventually led back to Moses).

The short answer -- the Gemara says that a student is not allowed to perform halachic rulings in the presence of his teacher unless he's been given permission. So one flavor of semicha is "I taught so-and-so, and I am now authorizing him to make his own rulings even when people could have gone to me instead." In this case, the "power" is having taught them.

Practically today, it's about communal recognition. Today's semicha began when a group of medieval rabbis felt that random unqualified people were taking pulpits, so they declared not to allow someone as a communal rabbi unless okayed by them. Similarly, everyone recognized Rabbi Moshe Feinstein as a massive halachic authority, so if he declared someone "ordained" and fit for a pulpit, people listened. It's actually not entirely clear (as far as I've read or asked around) whether he himself had an official "semicha" paper himself -- though his primary mentor, his father, had ordered him to start making rulings.