private static TableDescriptorBuilder changeConstraintEnabled(TableDescriptorBuilder builder,
    Class<? extends Constraint> clazz, boolean enabled) throws IOException {
    // get the original constraint
    Pair<String, String> entry = getKeyValueForClass(builder, clazz);
    if (entry == null) {
      throw new IllegalArgumentException("Constraint: " + clazz.getName()
        + " is not associated with this table. You can't enable it!");
    }

    // create a new configuration from that conf
    Configuration conf = readConfiguration(entry.getSecond());

    // set that it is enabled
    conf.setBoolean(ENABLED_KEY, enabled);

    // write it back out
    return writeConstraint(builder, entry.getFirst(), conf);
  }
Change the whether the constraint (if it is already present) is enabled or disabled.
hbase-server/src/main/java/org/apache/hadoop/hbase/constraint/Constraints.java