Can I use public security groups in cloud formation for ec2 launch configs?

Can I use public security groups in cloud formation for ec2 launch configs ? I am trying to simply direct the cloudformation stack to use an existing set and it fails to create those resources. I tried to create those security groups as a rolling set (ssh1,ssh2...) for each stack but no such luck either.

It would be really cool if your answer would include a code snippet as to how to do this exactly. thanks.