diff --git a/readme.md b/readme.md
index e24b650a..e5595bb0 100644
--- a/readme.md
+++ b/readme.md
@@ -28,7 +28,8 @@ import factory from '@js-entity-repos/express/dist/factory';
 
 const todosFacade = factory<TodoEntity>({
   // Optional property that modifies a filter for the service.
-  constructFilter: (filter) => {
+  constructFilter: ({ filter, req, res }) => {
+    // This is a great place to put authentication and authorisation logic.
     return filter;
   },
   // Optional property. Defaults to 10.
diff --git a/src/FacadeConfig.ts b/src/FacadeConfig.ts
index 892d90be..43c78371 100644
--- a/src/FacadeConfig.ts
+++ b/src/FacadeConfig.ts
@@ -1,10 +1,10 @@
 import Facade from '@js-entity-repos/core/dist/Facade';
 import Entity from '@js-entity-repos/core/dist/types/Entity';
-import Filter from '@js-entity-repos/core/dist/types/Filter';
+import FilterConstructor from './utils/FilterConstructor';
 import TransactionHandler from './utils/TransactionHandler';
 
 export default interface FacadeConfig<E extends Entity> {
-  readonly constructFilter: (filter: Filter<E>) => any;
+  readonly constructFilter: FilterConstructor<E>;
   readonly service: Facade<E>;
   readonly handleTransaction: TransactionHandler;
   readonly defaultPaginationLimit: number;
diff --git a/src/FactoryConfig.ts b/src/FactoryConfig.ts
index 2aae9cc6..4681ae96 100644
--- a/src/FactoryConfig.ts
+++ b/src/FactoryConfig.ts
@@ -1,10 +1,10 @@
 import Facade from '@js-entity-repos/core/dist/Facade';
 import Entity from '@js-entity-repos/core/dist/types/Entity';
-import { Filter } from '@js-entity-repos/core/dist/types/Filter';
+import FilterConstructor from './utils/FilterConstructor';
 import TransactionHandler from './utils/TransactionHandler';
 
 export default interface FactoryConfig<E extends Entity> {
-  readonly constructFilter?: (filter: Filter<E>) => any;
+  readonly constructFilter?: FilterConstructor<E>;
   readonly service: Facade<E>;
   readonly handleTransaction?: TransactionHandler;
   readonly defaultPaginationLimit?: number;
diff --git a/src/factory.ts b/src/factory.ts
index 5f867a0b..aa7bd93f 100644
--- a/src/factory.ts
+++ b/src/factory.ts
@@ -15,7 +15,7 @@ import handleTransaction from './utils/handleTransaction';
 
 export default <E extends Entity>(factoryConfig: FactoryConfig<E>): Router => {
   const facadeConfig: FacadeConfig<E> = {
-    constructFilter: (filter) => filter,
+    constructFilter: ({ filter }) => filter,
     defaultPaginationLimit: 10,
     handleTransaction,
     ...factoryConfig,
diff --git a/src/functions/countEntities.ts b/src/functions/countEntities.ts
index 5500fe6f..1271fe03 100644
--- a/src/functions/countEntities.ts
+++ b/src/functions/countEntities.ts
@@ -7,8 +7,9 @@ import getJsonQueryParam from '../utils/getJsonQueryParam';
 export default <E extends Entity>(config: FacadeConfig<E>) => {
   return async (req: Request, res: Response) => {
     await config.handleTransaction({ req, res }, async () => {
+      const filter = getJsonQueryParam(req.query, 'filter');
       const { count } = await config.service.countEntities({
-        filter: config.constructFilter(getJsonQueryParam(req.query, 'filter')),
+        filter: config.constructFilter({ filter, req, res }),
       });
       res.status(OK).json(count);
     });
diff --git a/src/functions/getEntities.ts b/src/functions/getEntities.ts
index 98718cd7..9bb477f8 100644
--- a/src/functions/getEntities.ts
+++ b/src/functions/getEntities.ts
@@ -8,9 +8,10 @@ import getNumberQueryParam from '../utils/getNumberQueryParam';
 export default <E extends Entity>(config: FacadeConfig<E>) => {
   return async (req: Request, res: Response) => {
     await config.handleTransaction({ req, res }, async () => {
+      const filter = getJsonQueryParam(req.query, 'filter');
       const limit = getNumberQueryParam(req.query, 'limit', config.defaultPaginationLimit);
       const result = await config.service.getEntities({
-        filter: config.constructFilter(getJsonQueryParam(req.query, 'filter')),
+        filter: config.constructFilter({ filter, req, res }),
         pagination: {
           cursor: req.query.cursor,
           forward: req.query.forward === 'true',
diff --git a/src/functions/getEntity.ts b/src/functions/getEntity.ts
index 0cc13324..b78a7603 100644
--- a/src/functions/getEntity.ts
+++ b/src/functions/getEntity.ts
@@ -7,8 +7,9 @@ import getJsonQueryParam from '../utils/getJsonQueryParam';
 export default <E extends Entity>(config: FacadeConfig<E>) => {
   return async (req: Request, res: Response) => {
     await config.handleTransaction({ req, res }, async () => {
+      const filter = getJsonQueryParam(req.query, 'filter');
       const { entity } = await config.service.getEntity({
-        filter: config.constructFilter(getJsonQueryParam(req.query, 'filter')),
+        filter: config.constructFilter({ filter, req, res }),
         id: req.params.id,
       });
       res.status(OK).json(entity);
diff --git a/src/functions/patchEntities.ts b/src/functions/patchEntities.ts
index f69a53a2..19472515 100644
--- a/src/functions/patchEntities.ts
+++ b/src/functions/patchEntities.ts
@@ -7,8 +7,9 @@ import getJsonQueryParam from '../utils/getJsonQueryParam';
 export default <E extends Entity>(config: FacadeConfig<E>) => {
   return async (req: Request, res: Response) => {
     await config.handleTransaction({ req, res }, async () => {
+      const filter = getJsonQueryParam(req.query, 'filter');
       const { entity } = await config.service.patchEntity({
-        filter: config.constructFilter(getJsonQueryParam(req.query, 'filter')),
+        filter: config.constructFilter({ filter, req, res }),
         id: req.params.id,
         patch: req.body,
       });
diff --git a/src/functions/removeEntities.ts b/src/functions/removeEntities.ts
index 8847191c..269451bc 100644
--- a/src/functions/removeEntities.ts
+++ b/src/functions/removeEntities.ts
@@ -7,8 +7,9 @@ import getJsonQueryParam from '../utils/getJsonQueryParam';
 export default <E extends Entity>(config: FacadeConfig<E>) => {
   return async (req: Request, res: Response) => {
     await config.handleTransaction({ req, res }, async () => {
+      const filter = getJsonQueryParam(req.query, 'filter');
       await config.service.removeEntities({
-        filter: config.constructFilter(getJsonQueryParam(req.query, 'filter')),
+        filter: config.constructFilter({ filter, req, res }),
       });
       res.status(NO_CONTENT).send();
     });
diff --git a/src/functions/removeEntity.ts b/src/functions/removeEntity.ts
index e41343d2..96c65ed2 100644
--- a/src/functions/removeEntity.ts
+++ b/src/functions/removeEntity.ts
@@ -7,8 +7,9 @@ import getJsonQueryParam from '../utils/getJsonQueryParam';
 export default <E extends Entity>(config: FacadeConfig<E>) => {
   return async (req: Request, res: Response) => {
     await config.handleTransaction({ req, res }, async () => {
+      const filter = getJsonQueryParam(req.query, 'filter');
       await config.service.removeEntity({
-        filter: config.constructFilter(getJsonQueryParam(req.query, 'filter')),
+        filter: config.constructFilter({ filter, req, res }),
         id: req.params.id,
       });
       res.status(NO_CONTENT).send();
diff --git a/src/functions/replaceEntity.ts b/src/functions/replaceEntity.ts
index 1c29ea50..79b2ddc9 100644
--- a/src/functions/replaceEntity.ts
+++ b/src/functions/replaceEntity.ts
@@ -7,9 +7,10 @@ import getJsonQueryParam from '../utils/getJsonQueryParam';
 export default <E extends Entity>(config: FacadeConfig<E>) => {
   return async (req: Request, res: Response) => {
     await config.handleTransaction({ req, res }, async () => {
+      const filter = getJsonQueryParam(req.query, 'filter');
       const { entity } = await config.service.replaceEntity({
         entity: req.body,
-        filter: config.constructFilter(getJsonQueryParam(req.query, 'filter')),
+        filter: config.constructFilter({ filter, req, res }),
         id: req.params.id,
       });
       res.status(OK).json(entity);
diff --git a/src/utils/FilterConstructor.ts b/src/utils/FilterConstructor.ts
new file mode 100644
index 00000000..2361fb51
--- /dev/null
+++ b/src/utils/FilterConstructor.ts
@@ -0,0 +1,13 @@
+import Entity from '@js-entity-repos/core/dist/types/Entity';
+import { Filter } from '@js-entity-repos/core/dist/types/Filter';
+import { Request, Response } from 'express';
+
+export interface Opts<E extends Entity> {
+  readonly req: Request;
+  readonly res: Response;
+  readonly filter: Filter<E>;
+}
+
+type FilterConstructor<E extends Entity> = (opts: Opts<E>) => Filter<E>;
+
+export default FilterConstructor;