是否可以更改ASP.NET MVC 3路由约束，以便它们返回带有JSON主体的400 Bad Request？

I am developing some REST resources using the ASP.NET MVC 3 platform. So far, its been great, I love the flexibility of MVC 3, and it is a breeze to build REST services with it. One area where I have been having a difficult time are the route constraints in Global.asax. For one, they never seem to work properly (including one ALWAYS returns 404, even if the input most definitely meets the requirements of the constraint...but thats another question). I am developing some REST resources using the A