diff --git a/stix2/test/v21/test_observed_data.py b/stix2/test/v21/test_observed_data.py
index 371018c..6f36d88 100644
--- a/stix2/test/v21/test_observed_data.py
+++ b/stix2/test/v21/test_observed_data.py
@@ -1538,39 +1538,3 @@ def test_deterministic_id_no_contributing_props():
     uuid_obj_2 = uuid.UUID(email_msg_2.id[-36:])
     assert uuid_obj_2.variant == uuid.RFC_4122
     assert uuid_obj_2.version == 4
-
-
-def test_ipv4_resolves_to_refs_deprecation():
-    with pytest.warns(stix2.exceptions.STIXDeprecationWarning):
-
-        stix2.v21.IPv4Address(
-            value="26.09.19.70",
-            resolves_to_refs=["mac-addr--08900593-0265-52fc-93c0-5b4a942f5887"],
-        )
-
-
-def test_ipv4_belongs_to_refs_deprecation():
-    with pytest.warns(stix2.exceptions.STIXDeprecationWarning):
-
-        stix2.v21.IPv4Address(
-            value="21.12.19.64",
-            belongs_to_refs=["autonomous-system--52e0a49d-d683-5801-a7b8-145765a1e116"],
-        )
-
-
-def test_ipv6_resolves_to_refs_deprecation():
-    with pytest.warns(stix2.exceptions.STIXDeprecationWarning):
-
-        stix2.v21.IPv6Address(
-            value="2001:0db8:85a3:0000:0000:8a2e:0370:7334",
-            resolves_to_refs=["mac-addr--08900593-0265-52fc-93c0-5b4a942f5887"],
-        )
-
-
-def test_ipv6_belongs_to_refs_deprecation():
-    with pytest.warns(stix2.exceptions.STIXDeprecationWarning):
-
-        stix2.v21.IPv6Address(
-            value="2001:0db8:85a3:0000:0000:8a2e:0370:7334",
-            belongs_to_refs=["autonomous-system--52e0a49d-d683-5801-a7b8-145765a1e116"],
-        )
diff --git a/stix2/v21/observables.py b/stix2/v21/observables.py
index 1703263..ed560a6 100644
--- a/stix2/v21/observables.py
+++ b/stix2/v21/observables.py
@@ -7,13 +7,10 @@ Observable and do not have a ``_type`` attribute.
 
 from collections import OrderedDict
 import itertools
-import warnings
 
 from ..base import _Extension, _Observable, _STIXBase
 from ..custom import _custom_extension_builder, _custom_observable_builder
-from ..exceptions import (
-    AtLeastOnePropertyError, DependentPropertiesError, STIXDeprecationWarning,
-)
+from ..exceptions import AtLeastOnePropertyError, DependentPropertiesError
 from ..properties import (
     BinaryProperty, BooleanProperty, DictionaryProperty,
     EmbeddedObjectProperty, EnumProperty, ExtensionsProperty, FloatProperty,
@@ -122,14 +119,6 @@ class DomainName(_Observable):
     ])
     _id_contributing_properties = ["value"]
 
-    def _check_object_constraints(self):
-        if self.get('resolves_to_refs'):
-            warnings.warn(
-                "The 'resolves_to_refs' property of domain-name is deprecated in "
-                "STIX 2.1. Use the 'resolves-to' relationship type instead",
-                STIXDeprecationWarning,
-            )
-
 
 class EmailAddress(_Observable):
     # TODO: Add link
@@ -421,21 +410,6 @@ class IPv4Address(_Observable):
     ])
     _id_contributing_properties = ["value"]
 
-    def _check_object_constraints(self):
-        if self.get('resolves_to_refs'):
-            warnings.warn(
-                "The 'resolves_to_refs' property of ipv4-addr is deprecated in "
-                "STIX 2.1. Use the 'resolves-to' relationship type instead",
-                STIXDeprecationWarning,
-            )
-
-        if self.get('belongs_to_refs'):
-            warnings.warn(
-                "The 'belongs_to_refs' property of ipv4-addr is deprecated in "
-                "STIX 2.1. Use the 'belongs-to' relationship type instead",
-                STIXDeprecationWarning,
-            )
-
 
 class IPv6Address(_Observable):
     # TODO: Add link
@@ -458,21 +432,6 @@ class IPv6Address(_Observable):
     ])
     _id_contributing_properties = ["value"]
 
-    def _check_object_constraints(self):
-        if self.get('resolves_to_refs'):
-            warnings.warn(
-                "The 'resolves_to_refs' property of ipv6-addr is deprecated in "
-                "STIX 2.1. Use the 'resolves-to' relationship type instead",
-                STIXDeprecationWarning,
-            )
-
-        if self.get('belongs_to_refs'):
-            warnings.warn(
-                "The 'belongs_to_refs' property of ipv6-addr is deprecated in "
-                "STIX 2.1. Use the 'belongs-to' relationship type instead",
-                STIXDeprecationWarning,
-            )
-
 
 class MACAddress(_Observable):
     # TODO: Add link