No point in repeating this check over multiple classes.

src/main/java/com/gmail/nossr50/party/commands/PartyChangeOwnerCommand.java

@@ -13,9 +13,6 @@ import com.gmail.nossr50.util.Permissions;
 import com.gmail.nossr50.util.Users;
 
 public class PartyChangeOwnerCommand implements CommandExecutor {
-    private Player player;
-    private Party playerParty;
-
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
         if (!Permissions.hasPermission(sender, "mcmmo.commands.party.owner")) {
@@ -25,16 +22,10 @@ public class PartyChangeOwnerCommand implements CommandExecutor {
 
         switch (args.length) {
         case 2:
-            player = (Player) sender;
-            playerParty = Users.getPlayer(player).getParty();
-
-            if (!playerParty.getLeader().equals(player.getName())) {
-                sender.sendMessage(LocaleLoader.getString("Party.NotOwner"));
-                return true;
-            }
+            Party playerParty = Users.getPlayer((Player) sender).getParty();
 
             if (!playerParty.getMembers().contains(mcMMO.p.getServer().getOfflinePlayer(args[1]))) {
-                player.sendMessage(LocaleLoader.getString("Party.NotInYourParty", args[1]));
+                sender.sendMessage(LocaleLoader.getString("Party.NotInYourParty", args[1]));
                 return true;
             }
 

src/main/java/com/gmail/nossr50/party/commands/PartyCommand.java

@@ -83,7 +83,13 @@ public class PartyCommand implements CommandExecutor {
         else if (args[0].equalsIgnoreCase("invite")) {
             return partyInviteCommand.onCommand(sender, command, label, args);
         }
-        else if (args[0].equalsIgnoreCase("kick")) {
+
+        if (!mcMMOPlayer.getParty().getLeader().equals(player.getName())) {
+            sender.sendMessage(LocaleLoader.getString("Party.NotOwner"));
+            return true;
+        }
+
+        if (args[0].equalsIgnoreCase("kick")) {
             return partyKickCommand.onCommand(sender, command, label, args);
         }
         else if (args[0].equalsIgnoreCase("disband")) {

src/main/java/com/gmail/nossr50/party/commands/PartyDisbandCommand.java

@@ -13,9 +13,6 @@ import com.gmail.nossr50.util.Permissions;
 import com.gmail.nossr50.util.Users;
 
 public class PartyDisbandCommand implements CommandExecutor {
-    private Player player;
-    private Party playerParty;
-
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
         if (!Permissions.hasPermission(sender, "mcmmo.commands.party.disband")) {
@@ -25,13 +22,7 @@ public class PartyDisbandCommand implements CommandExecutor {
 
         switch (args.length) {
         case 1:
-            player = (Player) sender;
-            playerParty = Users.getPlayer(player).getParty();
-
-            if (!playerParty.getLeader().equals(player.getName())) {
-                sender.sendMessage(LocaleLoader.getString("Party.NotOwner"));
-                return true;
-            }
+            Party playerParty = Users.getPlayer((Player) sender).getParty();
 
             for (Player member : playerParty.getOnlineMembers()) {
                 if (!PartyManager.handlePartyChangeEvent(member, playerParty.getName(), null, EventReason.KICKED_FROM_PARTY)) {

src/main/java/com/gmail/nossr50/party/commands/PartyKickCommand.java

@@ -15,9 +15,6 @@ import com.gmail.nossr50.util.Permissions;
 import com.gmail.nossr50.util.Users;
 
 public class PartyKickCommand implements CommandExecutor {
-    private Player player;
-    private Party playerParty;
-
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
         if (!Permissions.hasPermission(sender, "mcmmo.commands.party.kick")) {
@@ -27,13 +24,7 @@ public class PartyKickCommand implements CommandExecutor {
 
         switch (args.length) {
         case 2:
-            player = (Player) sender;
-            playerParty = Users.getPlayer(player).getParty();
-
-            if (!playerParty.getLeader().equals(player.getName())) {
-                sender.sendMessage(LocaleLoader.getString("Party.NotOwner"));
-                return true;
-            }
+            Party playerParty = Users.getPlayer((Player) sender).getParty();
 
             OfflinePlayer target = mcMMO.p.getServer().getOfflinePlayer(args[1]);
 
@@ -61,5 +52,4 @@ public class PartyKickCommand implements CommandExecutor {
             return true;
         }
     }
-
 }

src/main/java/com/gmail/nossr50/party/commands/PartyLockCommand.java

@@ -11,18 +11,11 @@ import com.gmail.nossr50.util.Permissions;
 import com.gmail.nossr50.util.Users;
 
 public class PartyLockCommand implements CommandExecutor {
-    private Player player;
     private Party playerParty;
 
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
-        player = (Player) sender;
-        playerParty = Users.getPlayer(player).getParty();
-
-        if (!playerParty.getLeader().equals(player.getName())) {
-            sender.sendMessage(LocaleLoader.getString("Party.NotOwner"));
-            return true;
-        }
+        playerParty = Users.getPlayer((Player) sender).getParty();
 
         switch (args.length) {
         case 1:
@@ -89,11 +82,11 @@ public class PartyLockCommand implements CommandExecutor {
         }
 
         if (!playerParty.isLocked()) {
-            player.sendMessage(LocaleLoader.getString("Party.IsntLocked"));
+            sender.sendMessage(LocaleLoader.getString("Party.IsntLocked"));
             return;
         }
 
         playerParty.setLocked(false);
-        player.sendMessage(LocaleLoader.getString("Party.Unlocked"));
+        sender.sendMessage(LocaleLoader.getString("Party.Unlocked"));
     }
 }