In one discussion, I think with my own lawyer when reviewing a proposed employment contract, I was advised that it is best to be quite specific about what is covered with these IP clauses precisely because how enforceable they are can ultimately come down to the unpredictable opinion of a court where the people making the decision might not be technical experts.
It was a long time ago, so I may be slightly misremembering the exact details, but in a nutshell the example given was someone who did have to hand something over because a court decided that being a salaried programmer using a certain programming language at work meant something they programmed in that same language at home was related to their employment. The software itself was in a totally different field to what they did for work, so their assumption had been that it wouldn't be covered, but the court didn't see it that way. I'm in England and was talking to an English lawyer about English employment, so I assume that was also the location of the case mentioned, but I'm afraid I don't know anything more specific to provide a proper citation.
I was also warned that this is a bigger problem for employees of huge companies with many divisions, because in that case the employer could have interests in a wide variety of different fields that would be relevant for contractual purposes. Even though any given employee might have no knowledge that something they're doing out-of-hours could be affected, because it's nothing to do with what they do themselves and what happens in their own part of the business, it can still be relevant from the employer's point of view and so trigger the contractual transfer of IP rights.
It was a long time ago, so I may be slightly misremembering the exact details, but in a nutshell the example given was someone who did have to hand something over because a court decided that being a salaried programmer using a certain programming language at work meant something they programmed in that same language at home was related to their employment. The software itself was in a totally different field to what they did for work, so their assumption had been that it wouldn't be covered, but the court didn't see it that way. I'm in England and was talking to an English lawyer about English employment, so I assume that was also the location of the case mentioned, but I'm afraid I don't know anything more specific to provide a proper citation.
I was also warned that this is a bigger problem for employees of huge companies with many divisions, because in that case the employer could have interests in a wide variety of different fields that would be relevant for contractual purposes. Even though any given employee might have no knowledge that something they're doing out-of-hours could be affected, because it's nothing to do with what they do themselves and what happens in their own part of the business, it can still be relevant from the employer's point of view and so trigger the contractual transfer of IP rights.