They can confiscate them, which is good, but they are discouraged from chasing them down. They don't want the bike/ATV rider to cause an accident while fleeing from the police.

I find it sadly ironic that some of the areas around Philly, where some residents were mocking our issues with these hordes of dirt bikes and ATVs swarming around, are now dealing with swarms of their own. It's not just in the city anymore.