$project_id = empty($_SESSION['selected_menu_item_id']) ? '' : 
    "tasks.project_id = ".$_SESSION['selected_menu_item_id']." AND";
$current_tasks_list_query = "SELECT
        tasks.id AS ID,
        tasks.name AS TASK_NAME,
        tasks.deadline_datetime AS TASK_DEADLINE,
        tasks.status AS TASK_STATUS,
        projects.name AS PROJECT_NAME
        FROM tasks 
        JOIN projects
        ON tasks.project_id = projects.id
        WHERE
        $project_id
        tasks.author_id = '".$USER['id']."'";

const NotAccess = (props) => {
  return (
    <div>
     Доступ закрыт
    </div>
  )
}

export default class RouteAdmin extends React.Component {
  constructor (props) {
    super(props)
    this.state = {
      component: null
    }
  }

  componentDidMount () {
    axios.post('/admin').then(data => data.data).then(data => {
      if (data.auth === true) {
        const Admin = React.lazy(() => import('./moduleAdmin/Index'))
        this.setState({component: Admin})
      } else {
        this.setState({component: NotAccess})
      }
    })
  }

  render () {
    const Component = this.state.component
    return (
      <Route path="/admin" {...this.props} render={this.state.component}/>
    )
  }
}

<Route path='/admin' render={props => <RouteAdmin {...path} />} />