A lot of venues (mostly lakes) ban pike fishing between March and October with live or dead baiting, but you can lure fish.
The reasoning behind this is that pike can suffer from low oxygen levels after a prolonged fight, and the stress can cause them to belly up and die.
Rivers the pike tend to be returned into higher oxygenated water, due to the flow.
Personally I save my piking from September onwards, unless I grab a lure session, which is not often. I do occasionally hook pike accidentally in the summer, usually when after perch where I may have been using a small livie for perch, or occasionally one snaffles a boilie or slug or a fish I'm retrieving.
On returning I am as careful as I can possibly be, holding onto the fish until it has recovered properly and swims away of its own accord.