diff --git a/config/checkstyle/checkstyle.xml b/config/checkstyle/checkstyle.xml
index a2d043d73..89177a84c 100644
--- a/config/checkstyle/checkstyle.xml
+++ b/config/checkstyle/checkstyle.xml
@@ -53,5 +53,19 @@
     <!-- <module name="PackageName"/> Unlikely that we would miss this in a PR -->
     <module name="ParameterName"/>
     <!-- <module name="TypeName"/> Unlikely that we would miss this in a PR -->
+    <!-- Validate assignment operators -->
+    <module name="WhitespaceAround">
+      <property name="tokens" value="ASSIGN"/>
+    </module>
+    <!-- Validate String.to(Lower|Upper)Case() calls include Locale argument -->
+    <module name="Regexp">
+      <property name="message" value="Case-conversion calls must include an explicit Locale"/>
+      <property name="format" value="(?!Character)\.to(Lower|Upper)Case\(\)"/>
+      <property name="illegalPattern" value="true"/>
+    </module>
+  </module>
+  <!-- Validate that command annotations are formatted correctly -->
+  <module name="RegexpMultiline">
+    <property name="format" value="^( +)@(Arg|Switch|Command)\(.*?\n\1 {5,}"/>
   </module>
 </module>
diff --git a/config/checkstyle/import-control.xml b/config/checkstyle/import-control.xml
index 28ccad1e4..a291b5ad5 100644
--- a/config/checkstyle/import-control.xml
+++ b/config/checkstyle/import-control.xml
@@ -16,6 +16,7 @@
   <allow pkg="net.royawesome.jlibnoise"/>
   <allow pkg="org.json.simple" />
   <allow pkg="org.slf4j"/>
+  <allow pkg="org.enginehub"/>
 
   <subpackage name="util.yaml">
     <allow pkg="org.yaml.snakeyaml"/>
@@ -38,11 +39,12 @@
   <subpackage name="worldedit">
     <allow pkg="org.mozilla.javascript"/>
     <allow pkg="de.schlichtherle"/>
+    <allow pkg="com.google.auto"/>
 
     <subpackage name="bukkit">
       <allow pkg="org.bukkit"/>
       <allow pkg="org.bstats.bukkit"/>
-      <allow pkg="net.minecraft.server"/>
+      <allow pkg="io.papermc.lib"/>
     </subpackage>
 
     <subpackage name="forge">
@@ -55,6 +57,7 @@
       <allow pkg="io.netty.buffer"/>
       <allow pkg="org.spongepowered.api" />
       <allow pkg="com.mojang.brigadier" />
+      <allow pkg="com.mojang.datafixers" />
     </subpackage>
 
     <subpackage name="sponge">