Ristrict change of state of work item based on state of another work item state
One answer
You would have to write a custom work item save advisor. Some advisor examples: https://rsjazz.wordpress.com/?s=advisor&submit=Search
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The blue thing in my answer is called a link. I would suggest following it to the examples.https://rsjazz.wordpress.com/2014/05/26/only-owner-can-close-workitem-advisor/ is a very simple example of an advisor that prevents work item state changes. You will have to do more in your advisor. You will have to locate the other work item and its state. How you can do that, depends on your special requirements. There are examples for these APIS on the blog as well. The blog features a search capability and tags that you can use to locate these posts. If you use links between the work items search for link-api or links. One of my very first blogs is around parent child links in an follow up action (aka participant, which is very similar to an advisor).