diff --git a/src/ConstraintGrader.fun b/src/ConstraintGrader.fun
new file mode 100644
index 0000000..5880e64
--- /dev/null
+++ b/src/ConstraintGrader.fun
@@ -0,0 +1,49 @@
+functor ConstraintGrader (
+  (* Constraint Grader should return 1.0 if no constraint was violated *)
+  structure Constraint : GRADER
+  structure Correctness : GRADER
+  val description : string
+  (* deduction is the fraction of the total points that will be deducted, this 
+   * should be Rational.one, as violating constraints deducts all points
+   *)
+  val deduction : Rational.t
+  val deductionMessage : string
+) :> GRADER =
+  struct
+    structure Rubric =
+      struct
+        val description = description
+
+        type t = Correctness.Rubric.t * Constraint.Rubric.t
+
+        fun toString (correctness, constraint) =
+          let
+            val passes = Rational.eq (Rational.one, Constraint.Rubric.score constraint)
+            val deductionPercent =
+              showPercentsUnweighted (if passes then Rational.zero else Rational.~ deduction, Rational.zero)
+            val deductionMessage = if passes then "" else deductionMessage
+          in
+            String.concat [
+              Correctness.Rubric.toString correctness,
+              deductionPercent ^ " " ^ Constraint.Rubric.description ^ "\n",
+              FormatUtil.indent (Constraint.Rubric.toString constraint),
+              FormatUtil.indent deductionMessage
+            ]
+          end
+
+        fun score (correctness, constraint) =
+          let
+            val correctnessScore = Correctness.Rubric.score correctness
+            val deduction =
+              if Rational.eq (Rational.one, Constraint.Rubric.score constraint)
+              then Rational.zero
+              else deduction
+          in
+            case (Rational.compare (correctnessScore, deduction)) of
+              LESS => Rational.zero
+            | _ => Rational.- (correctnessScore, deduction)
+          end
+      end
+
+    fun process () = (Correctness.process (), Constraint.process ())
+  end
diff --git a/src/FormatUtil.sml b/src/FormatUtil.sml
index 8653e7a..9c2db16 100644
--- a/src/FormatUtil.sml
+++ b/src/FormatUtil.sml
@@ -3,11 +3,14 @@ structure FormatUtil =
     local
       val padded = StringCvt.padLeft #" " 4 o Rational.percent
     in
-      val showPercents = fn (score,weight) =>
-        "(" ^ padded (Rational.* (weight,score)) ^
-        "/" ^ padded weight ^ "):"
+      val showPercentsUnweighted = fn (numerator, denominator) =>
+        "(" ^ padded numerator ^
+        "/" ^ padded denominator ^ "):"
     end
 
+    val showPercents = fn (score,weight) =>
+      showPercentsUnweighted (Rational.* (weight, score), weight)
+
     val indentWith = fn s0 =>
       let
         val spaces = String.implode (List.tabulate (String.size s0, Fn.const #" "))
diff --git a/src/sources.cm b/src/sources.cm
index 8d2c025..a03ea3d 100644
--- a/src/sources.cm
+++ b/src/sources.cm
@@ -19,6 +19,8 @@ Library
   functor EquivGraderBucketList
   functor EquivGraderList
 
+  functor ConstraintGrader
+
   functor Preamble
 
   structure FormatUtil
@@ -49,6 +51,8 @@ is
   EquivGraderBucket.fun
   EquivGrader.fun
 
+  ConstraintGrader.fun
+
   Preamble.fun
 
   FormatUtil.sml