diff --git a/src/blenderbim/blenderbim/bim/module/constraint/operator.py b/src/blenderbim/blenderbim/bim/module/constraint/operator.py
index 91315fedae..f461554c49 100644
--- a/src/blenderbim/blenderbim/bim/module/constraint/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/constraint/operator.py
@@ -205,18 +205,16 @@ class UnassignConstraint(bpy.types.Operator):
         return IfcStore.execute_ifc_operator(self, context)
 
     def _execute(self, context):
-        self.file = IfcStore.get_file()
+        self.file = tool.Ifc.get()
         objs = [bpy.data.objects.get(self.obj)] if self.obj else context.selected_objects
-        for obj in objs:
-            obj_id = obj.BIMObjectProperties.ifc_definition_id
-            if not obj_id:
-                continue
+        products = [self.file.by_id(obj_id) for obj in objs if (obj_id := obj.BIMObjectProperties.ifc_definition_id)]
+        if products:
             ifcopenshell.api.run(
                 "constraint.unassign_constraint",
                 self.file,
                 **{
-                    "product": self.file.by_id(obj_id),
+                    "products": products,
                     "constraint": self.file.by_id(self.constraint),
-                }
+                },
             )
         return {"FINISHED"}
diff --git a/src/blenderbim/blenderbim/core/resource.py b/src/blenderbim/blenderbim/core/resource.py
index 2d529c466a..63524cd03c 100644
--- a/src/blenderbim/blenderbim/core/resource.py
+++ b/src/blenderbim/blenderbim/core/resource.py
@@ -206,7 +206,7 @@ def remove_usage_constraint(ifc, resource_tool, resource, reference_path):
             reference = resource_tool.get_metric_reference(metric, is_deep=True)
             if reference == reference_path:
                 ifc.run("constraint.remove_metric", metric=metric)
-                ifc.run("constraint.unassign_constraint", product=resource, constraint=constraint)
+                ifc.run("constraint.unassign_constraint", products=[resource], constraint=constraint)
                 ifc.run("constraint.remove_constraint", constraint=constraint)
 
 
diff --git a/src/ifcopenshell-python/ifcopenshell/api/__init__.py b/src/ifcopenshell-python/ifcopenshell/api/__init__.py
index 07eec78914..f5a56279c0 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/__init__.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/__init__.py
@@ -114,6 +114,9 @@ ARGUMENTS_DEPRECATION = {
     "constraint.assign_constraint": partial(
         batching_argument_deprecation, prev_argument="product", new_argument="products"
     ),
+    "constraint.unassign_constraint": partial(
+        batching_argument_deprecation, prev_argument="product", new_argument="products"
+    ),
 }
 
 
diff --git a/src/ifcopenshell-python/ifcopenshell/api/constraint/unassign_constraint.py b/src/ifcopenshell-python/ifcopenshell/api/constraint/unassign_constraint.py
index 66b3bc94b9..dbc1e1b7fb 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/constraint/unassign_constraint.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/constraint/unassign_constraint.py
@@ -17,18 +17,24 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell
+import ifcopenshell.api
 import ifcopenshell.util.element
 
 
 class Usecase:
-    def __init__(self, file, product=None, constraint=None):
-        """Unassigns a constraint to a product
+    def __init__(
+        self,
+        file: ifcopenshell.file,
+        products: list[ifcopenshell.entity_instance],
+        constraint: ifcopenshell.entity_instance,
+    ):
+        """Unassigns a constraint from a list of products
 
         The constraint will not be deleted and is available to be assigned to
         other products.
 
-        :param product: The product the constraint applies to.
-        :type product: ifcopenshell.entity_instance.entity_instance
+        :param products: The list of products the constraint applies to.
+        :type products: list[ifcopenshell.entity_instance.entity_instance]
         :param constraint: The IfcObjective constraint
         :type constraint: ifcopenshell.entity_instance.entity_instance
         :return: None
@@ -36,14 +42,42 @@ class Usecase:
         """
         self.file = file
         self.settings = {
-            "product": product,
+            "products": products,
             "constraint": constraint,
         }
 
     def execute(self):
-        for rel in self.settings["product"].HasAssociations:
-            if rel.is_a("IfcRelAssociatesConstraint") and rel.RelatingConstraint == self.settings["constraint"]:
-                history = rel.OwnerHistory
-                self.file.remove(rel)
-                if history:
-                    ifcopenshell.util.element.remove_deep2(self.file, history)
+        products = set(self.settings["products"])
+        if not products:
+            return
+
+        self.constraint = self.settings["constraint"]
+        rels = self.get_constraint_rels()
+        related_objects = set()
+        for rel in rels:
+            related_objects.update(rel.RelatedObjects)
+
+        if not related_objects.intersection(products):
+            return
+
+        for rel in rels:
+            related_objects = set(rel.RelatedObjects)
+            if not related_objects.intersection(products):
+                continue
+            related_objects -= products
+            if related_objects:
+                rel.RelatedObjects = list(related_objects)
+                ifcopenshell.api.run("owner.update_owner_history", self.file, **{"element": rel})
+                continue
+
+            history = rel.OwnerHistory
+            self.file.remove(rel)
+            if history:
+                ifcopenshell.util.element.remove_deep2(self.file, history)
+
+    def get_constraint_rels(self) -> list[ifcopenshell.entity_instance]:
+        rels = []
+        for rel in self.file.get_inverse(self.constraint):
+            if rel.is_a("IfcRelAssociatesConstraint"):
+                rels.append(rel)
+        return rels
diff --git a/src/ifcopenshell-python/test/api/constraint/test_unassign_constraint.py b/src/ifcopenshell-python/test/api/constraint/test_unassign_constraint.py
new file mode 100644
index 0000000000..0d8a21b8bf
--- /dev/null
+++ b/src/ifcopenshell-python/test/api/constraint/test_unassign_constraint.py
@@ -0,0 +1,67 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2022 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import pytest
+import test.bootstrap
+import ifcopenshell.api
+import ifcopenshell.util.constraint
+
+
+class TestUnassignConstraint(test.bootstrap.IFC4):
+    def test_unassigning_a_constraint(self):
+        constraint = ifcopenshell.api.run("constraint.add_objective", self.file)
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        ifcopenshell.api.run(
+            "constraint.assign_constraint", self.file, products=[element, element2], constraint=constraint
+        )
+        ifcopenshell.api.run(
+            "constraint.unassign_constraint", self.file, products=[element, element2], constraint=constraint
+        )
+        assert ifcopenshell.util.constraint.get_constrained_elements(element) == set()
+        assert len(self.file.by_type("IfcRelAssociatesConstraint")) == 0
+
+    def test_doing_nothing_if_no_constraint(self):
+        constraint = ifcopenshell.api.run("constraint.add_objective", self.file)
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        ifcopenshell.api.run(
+            "constraint.unassign_constraint", self.file, products=[element, element2], constraint=constraint
+        )
+        assert ifcopenshell.util.constraint.get_constrained_elements(element) == set()
+        assert ifcopenshell.util.constraint.get_constrained_elements(element2) == set()
+
+    def test_updating_the_rel_when_a_reference_is_removed_with_multipled_elements(self):
+        constraint = ifcopenshell.api.run("constraint.add_objective", self.file)
+        element1 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element2 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        element3 = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        ifcopenshell.api.run("constraint.assign_constraint", self.file, products=[element1], constraint=constraint)
+        rel = self.file.by_type("IfcRelAssociatesConstraint")[0]
+
+        ifcopenshell.api.run(
+            "constraint.assign_constraint", self.file, products=[element2, element3], constraint=constraint
+        )
+        ifcopenshell.api.run(
+            "constraint.unassign_constraint", self.file, products=[element1, element2], constraint=constraint
+        )
+        assert rel.RelatedObjects == (element3,)
+
+
+class TestUnassignConstraintIFC2X3(test.bootstrap.IFC2X3, TestUnassignConstraint):
+    pass
diff --git a/src/ifcopenshell-python/test/api/test_api.py b/src/ifcopenshell-python/test/api/test_api.py
index 5d99932ba8..72d20392f3 100644
--- a/src/ifcopenshell-python/test/api/test_api.py
+++ b/src/ifcopenshell-python/test/api/test_api.py
@@ -298,3 +298,16 @@ class TestTemporarySupportForDeprecatedAPIArguments(test.bootstrap.IFC4):
         constraint = ifcopenshell.api.run("constraint.add_objective", self.file)
         ifcopenshell.api.run("constraint.assign_constraint", self.file, product=element, constraint=constraint)
         assert ifcopenshell.util.constraint.get_constrained_elements(constraint) == {element}
+
+    @deprecation_check
+    def test_unassigning_a_constraint(self):
+        constraint = ifcopenshell.api.run("constraint.add_objective", self.file)
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        ifcopenshell.api.run(
+            "constraint.assign_constraint", self.file, product=element, constraint=constraint
+        )
+        ifcopenshell.api.run(
+            "constraint.unassign_constraint", self.file, product=element, constraint=constraint
+        )
+        assert ifcopenshell.util.constraint.get_constrained_elements(element) == set()
+        assert len(self.file.by_type("IfcRelAssociatesConstraint")) == 0