National Labor Relations Board McCaskill asked to reveal position on micro-unions By Marshall Griffin • Jun 13, 2012 (via Flickr/Senator McCaskill) A group billing itself as non-partisan is calling on U.S. Senator Claire McCaskill (D, Missouri) to reveal where she stands on micro-unions. Micro-unions are smaller groups of workers within an officially-sanctioned labor union. The National Labor Relations Board (NRLB) issued a ruling last year that allowed the creation of micro-unions. Jason Klindt with the Coalition to Protect Missouri Jobs says micro-unions are a threat to small businesses.