Shield Broker

If the creature loses its shield counter during combat, it will be removed from combat when it changes controllers. If it hasn't already assigned combat damage by that time, it won't get to deal combat damage.

"Shield" is not an ability that creatures have and shield counters are not keyword counters. If a creature with a shield counter loses its abilities, the shield counter will still protect it as normal.

A creature with a shield counter on it may still be destroyed by state-based actions if it has damage marked on it equal to its toughness or has been dealt unpreventable damage by a source with deathtouch.