Can we create PO ECC for PR with external sourcing to SRM?

Dear SAP gurus,

We are in SRM 7.01 with backend ECC 6.05. Our deployment is classic scenario, and we are planning to use external requirement, where we will push non-sourced PR to SRM for sourcing.

As what we understand we need to code in ECC to determine what kind of PR will go to SRM and which ones will stay in ECC. My question is, if a PR already marked to be sourced to SRM, is it still possible for the buyer to create PO against this PR in ECC?

Best regards,

John