diff --git a/cerbos/client/permission_checker.go b/cerbos/client/permission_checker.go
index c1ccb8c..d86d81e 100644
--- a/cerbos/client/permission_checker.go
+++ b/cerbos/client/permission_checker.go
@@ -20,6 +20,10 @@ func NewPermissionChecker(service string, dashboardURL string) *PermissionChecke
 }
 
 func (p *PermissionChecker) CheckPermission(ctx context.Context, authInfo *appx.AuthInfo, resource string, action string) (bool, error) {
+	if p == nil {
+		return false, fmt.Errorf("permission checker not found")
+	}
+
 	if authInfo == nil {
 		return false, fmt.Errorf("auth info not found")
 	}
diff --git a/cerbos/client/permission_checker_utils.go b/cerbos/client/permission_checker_utils.go
deleted file mode 100644
index 33e80ae..0000000
--- a/cerbos/client/permission_checker_utils.go
+++ /dev/null
@@ -1,38 +0,0 @@
-package client
-
-import (
-	"context"
-
-	"github.com/reearth/reearthx/appx"
-	"github.com/reearth/reearthx/i18n"
-	"github.com/reearth/reearthx/rerror"
-)
-
-var (
-	errOperationDenied error = rerror.NewE(i18n.T("operation denied"))
-)
-
-type PermissionService interface {
-	CheckPermission(ctx context.Context, authInfo *appx.AuthInfo, resource string, action string) (bool, error)
-}
-
-func checkPermissionClient(client any) (PermissionService, bool) {
-	if client == nil {
-		return nil, false
-	}
-
-	adapter, ok := client.(PermissionService)
-	if !ok || adapter == nil {
-		return nil, false
-	}
-	return adapter, true
-}
-
-func CheckPermission(ctx context.Context, authInfo *appx.AuthInfo, client any, resource string, action string) (bool, error) {
-	checkPermissionAdapter, ok := checkPermissionClient(client)
-	if !ok {
-		return false, errOperationDenied
-	}
-
-	return checkPermissionAdapter.CheckPermission(ctx, authInfo, resource, action)
-}