diff --git a/composer.json b/composer.json
index 396c07d..13c454e 100644
--- a/composer.json
+++ b/composer.json
@@ -36,7 +36,8 @@
     },
     "require": {
         "php": "^8.1",
-        "simplesamlphp/assert": "^1.8",
+
+        "simplesamlphp/saml2": "~5.0.2",
         "simplesamlphp/simplesamlphp": "^2.4",
         "symfony/http-foundation": "^6.4"
     },
diff --git a/docs/authorize.md b/docs/authorize.md
index 9a7bb67..a4a719a 100644
--- a/docs/authorize.md
+++ b/docs/authorize.md
@@ -156,3 +156,21 @@ Additionally, some helpful instructions are shown.
     ],
 ],
 ```
+
+You can restrict an attribute allowance to a list of Service Providers.
+
+```php
+'authproc.sp' => [
+    60 => array[
+        'class' => 'authorize:Authorize',
+        'uid'   =>  [
+            '/.*@students.example.edu$/',
+            '/^(stu1|stu2|stu3)@example.edu$/',
+            'spEntityIDs' => [
+                'https://example.com/sp1',
+                'https://example.com/sp2'
+            ]
+        ]
+    ]
+]
+```
diff --git a/src/Auth/Process/Authorize.php b/src/Auth/Process/Authorize.php
index e9366b2..3c7bb80 100644
--- a/src/Auth/Process/Authorize.php
+++ b/src/Auth/Process/Authorize.php
@@ -4,10 +4,10 @@
 
 namespace SimpleSAML\Module\authorize\Auth\Process;
 
-use Exception;
-use SimpleSAML\Assert\Assert;
 use SimpleSAML\Auth;
+use SimpleSAML\Error;
 use SimpleSAML\Module;
+use SimpleSAML\SAML2\Assert\Assert;
 use SimpleSAML\Utils;
 
 use function array_diff;
@@ -61,6 +61,7 @@ class Authorize extends Auth\ProcessingFilter
     /**
      * Array of valid users. Each element is a regular expression. You should
      * use \ to escape special chars, like '.' etc.
+     * can also contain 'spEntityIDs' arrays to restrict rules to specific SPs.
      *
      * @var array<mixed>
      */
@@ -131,15 +132,32 @@ public function __construct(array $config, $reserved)
                 $arrayUtils = new Utils\Arrays();
                 $values = $arrayUtils->arrayize($values);
             } elseif (!is_array($values)) {
-                throw new Exception(sprintf(
+                throw new Error\Exception(sprintf(
                     'Filter Authorize: Attribute values is neither string nor array: %s',
                     var_export($attribute, true),
                 ));
             }
 
+            // Extract spEntityIDs if present
+            $spEntityIDs = null;
+            if (isset($values['spEntityIDs'])) {
+                Assert::isArray(
+                    $values['spEntityIDs'],
+                    sprintf(
+                        'Filter Authorize: spEntityIDs must be an array for attribute: %s',
+                        var_export($attribute, true),
+                    ),
+                    Error\Exception::class,
+                );
+                Assert::allValidEntityID($values['spEntityIDs']);
+
+                $spEntityIDs = $values['spEntityIDs'];
+                unset($values['spEntityIDs']);
+            }
+
             foreach ($values as $value) {
                 if (!is_string($value)) {
-                    throw new Exception(sprintf(
+                    throw new Error\Exception(sprintf(
                         'Filter Authorize: Each value should be a string for attribute: %s value: %s config: %s',
                         var_export($attribute, true),
                         var_export($value, true),
@@ -147,7 +165,11 @@ public function __construct(array $config, $reserved)
                     ));
                 }
             }
-            $this->valid_attribute_values[$attribute] = $values;
+
+            $this->valid_attribute_values[$attribute] = [
+                'values' => $values,
+                'spEntityIDs' => $spEntityIDs,
+            ];
         }
     }
 
@@ -171,9 +193,27 @@ public function process(array &$state): void
         }
         $state['authprocAuthorize_errorURL'] = $this->errorURL;
         $state['authprocAuthorize_allow_reauthentication'] = $this->allow_reauthentication;
+        // Get current SP EntityID from state
+        $currentSpEntityId = null;
+        if (isset($state['saml:sp:State']['core:SP'])) {
+            $currentSpEntityId = $state['saml:sp:State']['core:SP'];
+        } elseif (isset($state['Destination']['entityid'])) {
+            $currentSpEntityId = $state['Destination']['entityid'];
+        }
+
         $arrayUtils = new Utils\Arrays();
-        foreach ($this->valid_attribute_values as $name => $patterns) {
+        foreach ($this->valid_attribute_values as $name => $ruleConfig) {
             if (array_key_exists($name, $attributes)) {
+                $patterns = $ruleConfig['values'];
+                $spEntityIDs = $ruleConfig['spEntityIDs'];
+
+                // If spEntityIDs is specified, check if current SP is in the list
+                if ($spEntityIDs !== null) {
+                    if ($currentSpEntityId === null || !in_array($currentSpEntityId, $spEntityIDs, true)) {
+                        continue; // Skip this rule if SP is not specified or not in allowed list
+                    }
+                }
+
                 foreach ($patterns as $pattern) {
                     $values = $arrayUtils->arrayize($attributes[$name]);
                     foreach ($values as $value) {
diff --git a/tests/src/Auth/Process/AuthorizeTest.php b/tests/src/Auth/Process/AuthorizeTest.php
index a5e4755..27cd27f 100644
--- a/tests/src/Auth/Process/AuthorizeTest.php
+++ b/tests/src/Auth/Process/AuthorizeTest.php
@@ -240,4 +240,123 @@ public static function showUserAttributeScenarioProvider(): array
             [['uid' => 'stu3@example.edu', 'mail' => 'user@example.edu'], false, true, 'user@example.edu'],
         ];
     }
+
+    /**
+     * Test SP restriction functionality
+     *
+     * @param array $userAttributes The attributes to test
+     * @param string|null $spEntityId The SP Entity ID in the state
+     * @param bool $isAuthorized Should the user be authorized
+     */
+    #[DataProvider('spRestrictionScenarioProvider')]
+    public function testSpRestriction(array $userAttributes, ?string $spEntityId, bool $isAuthorized): void
+    {
+        $attributeUtils = new Utils\Attributes();
+        $userAttributes = $attributeUtils->normalizeAttributesArray($userAttributes);
+        $config = [
+            'uid' => [
+                '/.*@example.com$/',
+                'spEntityIDs' => [
+                    'https://sp1.example.com',
+                    'https://sp2.example.com',
+                ],
+            ],
+            'group' => [
+                '/^admins$/',
+                'spEntityIDs' => [
+                    'https://admin.example.com',
+                ],
+            ],
+        ];
+
+        $state = ['Attributes' => $userAttributes];
+        if ($spEntityId !== null) {
+            $state['saml:sp:State']['core:SP'] = $spEntityId;
+        }
+
+        $resultState = $this->processFilter($config, $state);
+        $resultAuthorized = isset($resultState['NOT_AUTHORIZED']) ? false : true;
+        $this->assertEquals($isAuthorized, $resultAuthorized);
+    }
+
+    /**
+     * @return array
+     */
+    public static function spRestrictionScenarioProvider(): array
+    {
+        return [
+            // Should be allowed - matching attribute and SP
+            [['uid' => 'user@example.com'], 'https://sp1.example.com', true],
+            [['uid' => 'user@example.com'], 'https://sp2.example.com', true],
+            [['group' => 'admins'], 'https://admin.example.com', true],
+
+            // Should be denied - matching attribute but wrong SP
+            [['uid' => 'user@example.com'], 'https://wrong.example.com', false],
+            [['group' => 'admins'], 'https://sp1.example.com', false],
+
+            // Should be denied - no SP specified but attribute would match
+            [['uid' => 'user@example.com'], null, false],
+            [['group' => 'admins'], null, false],
+
+            // Should be denied - wrong attribute regardless of SP
+            [['uid' => 'user@wrong.com'], 'https://sp1.example.com', false],
+            [['group' => 'users'], 'https://admin.example.com', false],
+        ];
+    }
+
+    /**
+     * Test mixed SP and non-SP rules
+     *
+     * @param array $userAttributes The attributes to test
+     * @param string|null $spEntityId The SP Entity ID in the state
+     * @param bool $isAuthorized Should the user be authorized
+     */
+    #[DataProvider('mixedRulesScenarioProvider')]
+    public function testMixedSpAndNonSpRules(array $userAttributes, ?string $spEntityId, bool $isAuthorized): void
+    {
+        $attributeUtils = new Utils\Attributes();
+        $userAttributes = $attributeUtils->normalizeAttributesArray($userAttributes);
+        $config = [
+            // Rule with SP restriction
+            'uid' => [
+                '/.*@restricted.com$/',
+                'spEntityIDs' => ['https://restricted.example.com'],
+            ],
+            // Rule without SP restriction (should work for all SPs)
+            'role' => [
+                '/^admin$/',
+                '/^superuser$/',
+            ],
+        ];
+
+        $state = ['Attributes' => $userAttributes];
+        if ($spEntityId !== null) {
+            $state['saml:sp:State']['core:SP'] = $spEntityId;
+        }
+
+        $resultState = $this->processFilter($config, $state);
+        $resultAuthorized = isset($resultState['NOT_AUTHORIZED']) ? false : true;
+        $this->assertEquals($isAuthorized, $resultAuthorized);
+    }
+
+    /**
+     * @return array
+     */
+    public static function mixedRulesScenarioProvider(): array
+    {
+        return [
+            // Should be allowed - role rule matches (no SP restriction)
+            [['role' => 'admin'], 'https://any.example.com', true],
+            [['role' => 'superuser'], null, true],
+
+            // Should be allowed - uid rule matches and SP is correct
+            [['uid' => 'user@restricted.com'], 'https://restricted.example.com', true],
+
+            // Should be denied - uid rule matches but SP is wrong
+            [['uid' => 'user@restricted.com'], 'https://other.example.com', false],
+
+            // Should be denied - no matching rules
+            [['uid' => 'user@other.com', 'role' => 'user'], 'https://any.example.com', false],
+        ];
+    }
 }