core-bundle/src/Resources/contao/dca/tl_image_size.php
public function checkPermission()
	{
		if ($this->User->isAdmin)
		{
			return;
		}

		if (!$this->User->hasAccess('image_sizes', 'themes'))
		{
			throw new Contao\CoreBundle\Exception\AccessDeniedException('Not enough permissions to access the image sizes module.');
		}
	}
public function checkPermission()
	{
		if ($this->User->isAdmin)
		{
			return;
		}

		if (!$this->User->hasAccess('image_sizes', 'themes'))
		{
			throw new Contao\CoreBundle\Exception\AccessDeniedException('Not enough permissions to access the image sizes module.');
		}
	}
Check permissions to edit the table

@throws Contao\CoreBundle\Exception\AccessDeniedException