diff --git a/fml/src/main/java/cpw/mods/fml/common/asm/transformers/TerminalTransformer.java b/fml/src/main/java/cpw/mods/fml/common/asm/transformers/TerminalTransformer.java
index b8707168f..ec62cd2e5 100644
--- a/fml/src/main/java/cpw/mods/fml/common/asm/transformers/TerminalTransformer.java
+++ b/fml/src/main/java/cpw/mods/fml/common/asm/transformers/TerminalTransformer.java
@@ -1,12 +1,113 @@
 package cpw.mods.fml.common.asm.transformers;
 
+import org.objectweb.asm.*;
+
+import cpw.mods.fml.relauncher.FMLRelaunchLog;
+import cpw.mods.fml.relauncher.FMLSecurityManager.ExitTrappedException;
 import net.minecraft.launchwrapper.IClassTransformer;
 
-public class TerminalTransformer implements IClassTransformer {
+public class TerminalTransformer implements IClassTransformer
+{
     @Override
     public byte[] transform(String name, String transformedName, byte[] basicClass)
     {
-        return basicClass;
+        ClassReader reader = new ClassReader(basicClass);
+        ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS);
+
+        ClassVisitor visitor = writer;
+        visitor = new ExitVisitor(visitor);
+
+        reader.accept(visitor, 0);
+        return writer.toByteArray();
     }
 
+    public static class ExitVisitor extends ClassVisitor
+    {
+        private String clsName = null;
+        private static final String callbackOwner = org.objectweb.asm.Type.getInternalName(ExitVisitor.class);
+
+        private ExitVisitor(ClassVisitor cv)
+        {
+            super(Opcodes.ASM4, cv);
+        }
+
+        @Override
+        public void visit(int version, int access, String name, String signature, String superName, String[] interfaces)
+        {
+            super.visit(version, access, name, signature, superName, interfaces);
+            this.clsName = name;
+        }
+
+        @Override
+        public MethodVisitor visitMethod(int mAccess, final String mName, final String mDesc, String mSignature, String[] mExceptions)
+        {
+            final boolean warn = !clsName.equals("net/minecraft/client/Minecraft") &&
+                                 !clsName.equals("net/minecraft/server/dedicated/DedicatedServer") &&
+                                 !clsName.equals("cpw/mods/fml/common/FMLCommonHandler");
+
+            return new MethodVisitor(Opcodes.ASM4, super.visitMethod(mAccess, mName, mDesc, mSignature, mExceptions))
+            {
+                public void visitMethodInsn(int opcode, String owner, String name, String desc)
+                {
+                    if (opcode == Opcodes.INVOKESTATIC && owner.equals("java/lang/System") && name.equals("exit") && desc.equals("(I)V"))
+                    {
+                        if (warn)
+                        {
+                            FMLRelaunchLog.warning("=============================================================");
+                            FMLRelaunchLog.warning("MOD HAS DIRECT REFERENCE System.exit() THIS IS NOT ALLOWED REROUTING TO FMLCommonHandler!");
+                            FMLRelaunchLog.warning("Offendor: %s.%s%s", ExitVisitor.this.clsName, mName, mDesc);
+                            FMLRelaunchLog.warning("=============================================================");
+                        }
+                        owner = ExitVisitor.callbackOwner;
+                        name = "systemExitCalled";
+                    }
+                    else if (opcode == Opcodes.INVOKEVIRTUAL && owner.equals("java/lang/Runtime") && name.equals("exit") && desc.equals("(I)V"))
+                    {
+                        if (warn)
+                        {
+                            FMLRelaunchLog.warning("=============================================================");
+                            FMLRelaunchLog.warning("MOD HAS DIRECT REFERENCE Runtime.exit() THIS IS NOT ALLOWED REROUTING TO FMLCommonHandler!");
+                            FMLRelaunchLog.warning("Offendor: %s.%s%s", ExitVisitor.this.clsName, mName, mDesc);
+                            FMLRelaunchLog.warning("=============================================================");
+                        }
+                        opcode = Opcodes.INVOKESTATIC;
+                        owner = ExitVisitor.callbackOwner;
+                        name = "runtimeExitCalled";
+                        desc = "(Ljava/lang/Runtime;I)V";
+                    }
+
+                    super.visitMethodInsn(opcode, owner, name, desc);
+                }
+            };
+        }
+
+        // Intercept System.exit, and check if the caller is allowed to use it, if not wrap it in a ExitTrappedException
+        public static void systemExitCalled(int status)
+        {
+            ExitVisitor.checkAccess();
+            System.exit(status);
+        }
+        // Intercept Runtime.getRuntime().exit, and check if the caller is allowed to use it, if not wrap it in a ExitTrappedException
+        public static void runtimeExitCalled(Runtime runtime, int status)
+        {
+            ExitVisitor.checkAccess();
+            runtime.exit(status);
+        }
+
+        private static void checkAccess()
+        {
+            StackTraceElement[] cause = Thread.currentThread().getStackTrace();
+
+            String callingClass = cause.length > 2 ? cause[3].getClassName() : "none";
+            String callingParent = cause.length > 3 ? cause[4].getClassName() : "none";
+            // FML is allowed to call system exit and the Minecraft applet (from the quit button), and the dedicated server (from itself)
+            if (!(callingClass.startsWith("cpw.mods.fml.") ||
+                 ("net.minecraft.client.Minecraft".equals(callingClass) && "net.minecraft.client.Minecraft".equals(callingParent)) ||
+                 ("net.minecraft.server.dedicated.DedicatedServer".equals(callingClass) && "net.minecraft.server.MinecraftServer".equals(callingParent)))
+               )
+            {
+                throw new ExitTrappedException();
+            }
+        }
+    }
 }