Saving a unity scene when it's a read only file?

Hello, I'm working on setting up our project work flow for my company and I ran across an issue that I hope someone else has seen. Basically trying to get a form of scene management going we used SVN's locking and unlocking system to only allow 1 person access to a scene at a time (the lock makes the file read only). However, unity seems to be able to save over read only scene files. This is on windows. Is there a option in the editor to stop this from happening or has anyone found a way to do this?