Can I remove security door without tenant's agreement?

[Jina Lee]

I live in a duplex that I own in Los Angeles. I purchased this property about a year ago, and the tenant had been living there for a long time.

Originally, there was a security door, and the entry doors of each unit were side by side inside the security door. Then I moved my entry door to the other side of the building because I wanted more privacy.

There is a little space between the screen security door and the tenant's entry unit, which originally was common area. But after I moved my entrance, my tenant only passes the space. Then they started to keep their belongings in the space, which I didn't mind at the beginning, but recently I see they leave dangerous items such as burning candles and a standing mirror without mounting. I find it dangerous because the door is screen, and delivery would be placed in that space. So I casually requested to remove them but they ignored it..  

Now I am going to give them a formal notice to remove their belongings, but at the same time, I would like to just remove the security door. In my neighborhood, not many houses or rental units have security door including the unit I am living at.

But I wonder if this is something that I need to give tenants notice? should I get an agreement? and something I should get permission by LA Housing department first?