How can I use iptables to block certain processes from accessing the network?

Question

I can set the processes to run under special uid's and use the technique from this SF answer:

 -A OUTPUT -m owner --uid-owner 400 -j DROP

...But are there any other ways to blacklist based on the PID or its parent's PID without setting up new user accounts?

Relevant links:

• Blocking outgoing connects with iptables

EDIT:

A possible duplicate of Block network access of a process?

EDIT #2:

unshare -n doesn't work on CentOS/RHEL 6.5, since the kernel is compiled without CONFIG_NET_NS=Y.