Who confirms US Supreme Court decisions?

The Senate (Legislative Branch) must confirm a President's nomination to the US Supreme Court by a simple majority vote (51% of those present), under the Constitution's "advice and consent" clause. If the nominee is filibustered, cloture (ending the filibuster) requires a three-fifths (60) vote. (As of 1975, Senate Rule 22 no longer requires a two-thirds supermajority to end a filibuster)