Specification says that you should not use non-final static fields, but I
don't know any EJB container where deploying the bean with such a field
results in an error. Why mark this as an error, then?
Don't try to make IDEA to check every statement in EJB specification and
mark non-compliant code with errors. IMHO, you should mark only the errors
that will prevent the successful deployment of the code (like in java source
code -- you should mark only errors that will prevent code complication).