Town councillor: The only reason for the town to have ordinances restricting where skateboarding can be done would be to protect children from danger.
Conclusion
The town should not pass an ordinance prohibiting skateboarding in River Park.
Evidence
(1) The only reason for the town to restrict skateboarding would be to protect children from danger. (2) Park skateboarding is dangerous, but if banned, children will skateboard in the streets. (3) Street skateboarding is more dangerous than park skateboarding.
Evaluate
The argument's logic: enacting the ban would push children to a more dangerous alternative. So the ordinance — meant to protect children from danger — would actually expose them to greater danger. The principle that bridges the evidence and conclusion needs to capture this logic: don't enact a danger-reducing ordinance if it would produce greater danger.
Goal
Find a principle that says: ordinances meant to eliminate dangers should not be enacted when they would lead to greater dangers. That principle, plus the councillor's evidence, gives the conclusion.