diff --git a/core/modules/book/book.module b/core/modules/book/book.module
index d0aa9b0..4c62274 100644
--- a/core/modules/book/book.module
+++ b/core/modules/book/book.module
@@ -82,7 +82,8 @@ function book_entity_type_build(array &$entity_types) {
   $entity_types['node']
     ->setFormClass('book_outline', 'Drupal\book\Form\BookOutlineForm')
     ->setLinkTemplate('book-outline-form', '/node/{node}/outline')
-    ->setLinkTemplate('book-remove-form', '/node/{node}/outline/remove');
+    ->setLinkTemplate('book-remove-form', '/node/{node}/outline/remove')
+    ->addConstraint('BookOutline', []);
 }
 
 /**
diff --git a/core/modules/book/src/BookManager.php b/core/modules/book/src/BookManager.php
index 03ff784..402776c 100644
--- a/core/modules/book/src/BookManager.php
+++ b/core/modules/book/src/BookManager.php
@@ -278,36 +278,8 @@ public function updateOutline(NodeInterface $node) {
 
     // Prevent changes to the book outline if the node being saved is not the
     // default revision.
-    // @todo Convert this to an entity constraint in
-    //   https://www.drupal.org/node/2883868.
     $updated = !$new && (($original = $this->loadBookLink($node->id(), FALSE)) && ($node->book['bid'] != $original['bid'] || $node->book['pid'] != $original['pid']));
     if (($new || $updated) && !$node->isDefaultRevision()) {
-      drupal_set_message($this->t('This is not the default revision. You can only change the book outline for the <em>published</em> version of this content.'), 'error');
-
-      // Improve the usability of the error message by showing the changes that
-      // could not be applied.
-      if ($updated) {
-        $changes = [];
-        $new_parents = $this->loadBookLinks([$node->book['bid'], $node->book['pid']]);
-        if ($node->book['bid'] != $original['bid'] && $new_parents[$node->book['bid']]['access']) {
-          $changes[] = $this->t('The book was not changed to %book_label', ['%book_label' => $new_parents[$node->book['bid']]['title']]);
-        }
-        if ($node->book['pid'] != $original['pid'] && $new_parents[$node->book['pid']]['access']) {
-          $changes[] = $this->t('The parent was not changed to %parent_label', ['%parent_label' => $new_parents[$node->book['pid']]['title']]);
-        }
-
-        $message = [
-          [
-            '#markup' => $this->t('The following changes were not applied:')
-          ],
-          [
-            '#theme' => 'item_list',
-            '#items' => $changes,
-          ]
-        ];
-        drupal_set_message($this->renderer->renderPlain($message), 'warning');
-      }
-
       return FALSE;
     }
 
diff --git a/core/modules/book/src/Plugin/Validation/Constraint/BookOutlineConstraint.php b/core/modules/book/src/Plugin/Validation/Constraint/BookOutlineConstraint.php
new file mode 100644
index 0000000..677d36c
--- /dev/null
+++ b/core/modules/book/src/Plugin/Validation/Constraint/BookOutlineConstraint.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Drupal\book\Plugin\Validation\Constraint;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * Validation constraint for changing the book outline in forward revisions.
+ *
+ * @Constraint(
+ *   id = "BookOutline",
+ *   label = @Translation("Book outline.", context = "Validation"),
+ * )
+ */
+class BookOutlineConstraint extends Constraint {
+
+  public $message = 'This is not the default revision. You can only change the book outline for the <em>published</em> version of this content.';
+
+}
diff --git a/core/modules/book/src/Plugin/Validation/Constraint/BookOutlineConstraintValidator.php b/core/modules/book/src/Plugin/Validation/Constraint/BookOutlineConstraintValidator.php
new file mode 100644
index 0000000..66ff644
--- /dev/null
+++ b/core/modules/book/src/Plugin/Validation/Constraint/BookOutlineConstraintValidator.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Drupal\book\Plugin\Validation\Constraint;
+
+use Drupal\book\BookManagerInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Constraint validator for changing the book outline in forward revisions.
+ */
+class BookOutlineConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * Creates a new BookOutlineConstraintValidator instance.
+   *
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The book manager.
+   */
+  public function __construct(BookManagerInterface $book_manager) {
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('book.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validate($entity, Constraint $constraint) {
+    if (isset($entity) && !$entity->isNew() && !$entity->isDefaultRevision()) {
+      /** @var \Drupal\Core\Entity\ContentEntityInterface $original */
+      $original = $this->bookManager->loadBookLink($entity->id(), FALSE);
+      if ($entity->book['bid'] != $original['bid'] || $entity->book['pid'] != $original['pid']) {
+        $this->context->buildViolation($constraint->message)
+          ->setInvalidValue($entity)
+          ->addViolation();
+      }
+    }
+  }
+
+}