enforce a bandwidth limit for scp per user
 

When using scp to transfer files, I can use the "-l" option to limit the bandwidth of the file transfer.

Now I have a ssh/scp server running.
I want to enforce a bandwidth limit for scp per user.

How should I do this?

You could make a command alias.
Different distributions handle this in different ways. My PCLOS system has a script /etc/profile.d/alias.sh which contains commands that are executed when anyone logs in. Aliases are defined like that. Other methods used on UNIX and Linux systems include putting log in commands in /etc/bash.local or in each person's $HOME/.bashrc or $HOME/.alias.