WASHINGTON — It’s clearly illegal to hack into someone else’s computer network and steal information from it. But what about a police officer who uses his own department’s computer database to look up women from his past? Or an employee who uses his log-in credentials to download confidential information from his employer? These are questions that for years have vexed the courts, which have struggled to define the difference between permissible and illegal computer use.Stung by recent court decisions that have gone against …