diff --git a/src/Service/Project/ProjectService.php b/src/Service/Project/ProjectService.php
new file mode 100644
index 0000000..375c4d7
--- /dev/null
+++ b/src/Service/Project/ProjectService.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace App\Service\Project;
+
+use App\Entity\Project\Project;
+use App\Entity\Project\ProjectStatus;
+use App\Entity\User\User;
+use App\Security\Voter\UserOwnedVoterTrait;
+
+class ProjectService
+{
+    use UserOwnedVoterTrait;
+
+    public const OWNER_VALID_TRANSITIONS = [
+        ProjectStatus::InDraft->value => [ProjectStatus::ToCampaignReview],
+        ProjectStatus::InCampaignReviewToChange->value => [ProjectStatus::InCampaignReviewToReview],
+        ProjectStatus::ToCampaign->value => [ProjectStatus::InCampaign],
+        ProjectStatus::InFundingReviewToChange->value => [ProjectStatus::InFundingReviewToReview],
+        ProjectStatus::ToFunding->value => [ProjectStatus::InFunding],
+    ];
+
+    /**
+     * Check if an User can move a Project to some status.
+     *
+     * @param User          $actor   The User that is to apply the status change
+     * @param Project       $project The Project in their current (pre-change) state
+     * @param ProjectStatus $to      The ProjectStatus that the actor wishes to move the Project to
+     */
+    public function canTransition(User $actor, Project $project, ProjectStatus $to): bool
+    {
+        if ($actor->hasRoles(['ROLE_ADMIN'])) {
+            return true;
+        }
+
+        if (!$this->isOwnerOf($project, $actor)) {
+            return false;
+        }
+
+        $from = $project->getStatus();
+
+        if (
+            array_key_exists($from->value, self::OWNER_VALID_TRANSITIONS)
+            && in_array($to, self::OWNER_VALID_TRANSITIONS[$from->value])
+        ) {
+            return true;
+        }
+
+        return false;
+    }
+}
diff --git a/src/State/Project/ProjectStateProcessor.php b/src/State/Project/ProjectStateProcessor.php
index 53cd38b..3273b4b 100644
--- a/src/State/Project/ProjectStateProcessor.php
+++ b/src/State/Project/ProjectStateProcessor.php
@@ -2,6 +2,7 @@
 
 namespace App\State\Project;
 
+use ApiPlatform\Metadata\Exception\AccessDeniedException;
 use ApiPlatform\Metadata\Operation;
 use ApiPlatform\State\ProcessorInterface;
 use App\ApiResource\Project\ProjectApiResource;
@@ -10,6 +11,7 @@ use App\Dto\ProjectUpdationDto;
 use App\Entity\Project\Project;
 use App\Entity\Project\ProjectCalendar;
 use App\Mapping\AutoMapper;
+use App\Service\Project\ProjectService;
 use App\State\EntityStateProcessor;
 use Symfony\Bundle\SecurityBundle\Security;
 use Symfony\Component\Security\Core\Exception\AuthenticationException;
@@ -20,22 +22,20 @@ class ProjectStateProcessor implements ProcessorInterface
         private EntityStateProcessor $entityStateProcessor,
         private AutoMapper $autoMapper,
         private Security $security,
+        private ProjectService $projectService,
     ) {}
 
     /**
      * @param ProjectCreationDto|ProjectUpdationDto $data
-     * @param array{id: int}                        $uriVariables
-     *
-     * @return ProjectApiResource|null
      */
     public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = [])
     {
         if ($data instanceof ProjectCreationDto) {
             $project = $this->getProjectFromCreation($data);
-        }
-
-        if ($data instanceof ProjectUpdationDto) {
-            $project = $this->getProjectFromUpdate($data, $uriVariables);
+        } elseif ($data instanceof ProjectUpdationDto) {
+            $project = $this->getProjectFromUpdate($data, $context);
+        } else {
+            throw new \InvalidArgumentException('Unsupported input for Project resource');
         }
 
         $project = $this->entityStateProcessor->process($project, $operation, $uriVariables, $context);
@@ -72,13 +72,27 @@ class ProjectStateProcessor implements ProcessorInterface
         return $project;
     }
 
-    private function getProjectFromUpdate(ProjectUpdationDto $data, array $uriVariables): Project
+    private function getProjectFromUpdate(ProjectUpdationDto $data, array $context): Project
     {
-        $data = $this->autoMapper->map($uriVariables, $data);
-
         /** @var Project */
-        $project = $this->autoMapper->map($data, Project::class);
+        $project = $this->autoMapper->map($context['previous_data'], Project::class);
 
-        return $project;
+        $actor = $this->security->getUser();
+
+        if (!$actor) {
+            throw new AuthenticationException();
+        }
+
+        if ($data->status !== $project->getStatus()) {
+            if (!$this->projectService->canTransition($actor, $project, $data->status)) {
+                throw new AccessDeniedException(\sprintf(
+                    "Cannot move the Project from status '%s' to '%s'",
+                    $project->getStatus()->value,
+                    $data->status->value
+                ));
+            }
+        }
+
+        return $this->autoMapper->map($data, $project);
     }
 }