You will need to check your rental agreement or the lease you signed with the managers for anything that says they can do this.
Assuming there is nothing in the contract that allows this, then you should have full rights to the carport space as part of your rent due each month. This means towing anyone out of your spot, but first you may want to put a note on their car warning them, and you may want to post a "no parking" sign as well.
If it happens after you take these steps, then tow them.