I need an answer
 

I have a question and I hope I will find an aswer to it.
I hold a JAA CPL/IR with a multi-engine rating and I am studying for my ATPL frozen.
My total time is 1000 hrs and I would like to know if there is any JAA regulation that doesn't allow me to fly in an airline as a SIC.
I know that with my qualifications I do need a MCC but I am not sure if I need the ATPL frozen to be able to log hrs as SIC in a multi crew operated a/c.

If you have an aswer please I will be glad if you also show me where I can check.

Thank you

In order to fly for an airline you are likely to need a multi-pilot airplane type rating,and according to JAR-FCL1.250 there are 4
pre-requisite conditions to complete a MPA type rating:

1.have at least 100 hours as pilot-in-command of airplanes.
2.have a valid multi-engine instrument rating
3.hold a MCC certificate
4.have JAA ATPL theory

Having said that, it looks like you are missing the last two conditions and I can not see how you can log hours on a multi-pilot airplane without a type rating.