babel 7 Using the export keyword between a decorator and a class is not allowed. Please use `export @dec class` instead

Instead of changing the import statements across your project, you could use the legacyDecorators option in your .eslintrc file.

{    
  "parserOptions": {
     "ecmaFeatures": {
       "legacyDecorators": true
     }
   }
}

There is a work around you can do. Modify your class to the following.

import React, { Component } from 'react';
import { observer,inject } from 'mobx-react'

import './style.scss'

@inject('routingStore', 'UserStore')
@observer
class Login extends Component {
  constructor(props) {
    super(props);
    this.state = {};
  }

  render() {
    return (
        <div>
            <h1>Login</h1>
        </div>
      );
    }
  }

export default Login;

Technically, you just move export to the bottom of the class. If you have a lot of classes, that solution is not the best one. I couldn't find better way, yet.