diff --git a/.flake8 b/.flake8
index 7584aa6..eb84764 100644
--- a/.flake8
+++ b/.flake8
@@ -1,5 +1,5 @@
 [flake8]
 max-line-length = 100
-ignore = E251, E265, E261, E302
+ignore = E251, E265, E261, E302, W503
 per-file-ignores = __init__.py:F401
-exclude = server/tests/conftest.py
\ No newline at end of file
+exclude = server/tests/conftest.py
diff --git a/server/npg/porch/models/permission.py b/server/npg/porch/models/permission.py
new file mode 100644
index 0000000..f4d1cd9
--- /dev/null
+++ b/server/npg/porch/models/permission.py
@@ -0,0 +1,50 @@
+# Copyright (C) 2021, 2022 Genome Research Ltd.
+#
+# Author: Kieron Taylor kt19@sanger.ac.uk
+# Author: Marina Gourtovaia mg8@sanger.ac.uk
+#
+# This file is part of npg_porch
+#
+# npg_porch is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the Free
+# Software Foundation; either version 3 of the License, or (at your option) any
+# later version.
+#
+# This program 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 General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program. If not, see <http://www.gnu.org/licenses/>.
+
+from enum import Enum
+from pydantic import BaseModel, Field, validator
+from typing import Optional
+
+from npg.porch.models.pipeline import Pipeline
+
+class RolesEnum(str, Enum):
+    POWER_USER = 'power_user'
+    REGULAR_USER = 'regular_user'
+
+class Permission(BaseModel):
+    pipeline: Optional[Pipeline] = Field(
+        None,
+        title = 'An optional pipeline object',
+        description = 'The scope is limited to this pipeline if undefined'
+    )
+    requestor_id: int = Field(
+        title = 'ID that corresponds to the presented credentials',
+        description = 'A validated internal ID that corresponds to the presented credentials'
+    )
+    role: RolesEnum = Field(
+        title = 'A role associated with the presented credentials',
+    )
+
+    @validator('role')
+    def no_pipeline4special_users(cls, v, values):
+        if (v == RolesEnum.POWER_USER
+                and ('pipeline' in values and values['pipeline'] is not None)):
+            raise ValueError('Power user cannot be associated with a pipeline')
+        return v
diff --git a/server/tests/model_permission_test.py b/server/tests/model_permission_test.py
new file mode 100644
index 0000000..ff103e5
--- /dev/null
+++ b/server/tests/model_permission_test.py
@@ -0,0 +1,46 @@
+import pytest
+
+from npg.porch.models.pipeline import Pipeline
+from npg.porch.models.permission import Permission
+from pydantic.error_wrappers import ValidationError
+
+def test_model_create():
+    ''''
+    Test objects can be created.
+    '''
+
+    p = Permission(requestor_id = 3, role = 'power_user')
+    assert type(p) is Permission
+    p = Permission(
+        requestor_id = 1,
+        role = 'regular_user',
+        pipeline = Pipeline(name='number one')
+    )
+    assert type(p) is Permission
+
+def test_xvalidation_role_pipeline():
+    '''
+    Test cross validation for the role and pipeline fields.
+    '''
+
+    with pytest.raises(
+            ValidationError,
+            match = r'Power user cannot be associated with a pipeline'):
+        Permission(
+            requestor_id = 3,
+            role = 'power_user',
+            pipeline = Pipeline(name='number one')
+        )
+
+def test_error_with_insufficient_args():
+
+    with pytest.raises(ValidationError, match=r'requestor_id\s+field required'):
+        Permission(
+            role = 'regular_user',
+            pipeline = Pipeline(name='number one')
+        )
+    with pytest.raises(ValidationError, match=r'role\s+field required'):
+        Permission(
+            requestor_id = 1,
+            pipeline = Pipeline(name='number one')
+        )