As Oliver enters the police station to turn himself in the first cop that notices him draws his pistol twice. the first time is when the camera p.o.v. is on Oliver's back side. the second is with p.o.v. on Oliver's face.
Captain Lance issues an arrest warrant for Oliver Queen, following the recent murders of the "Arrow". However, given that Ra's told Lance Oliver was the Arrow with no solo proof, Captain Lance should have not been able to issue an arrest warrant, let alone doing that without evidence.
When Ray is in the hospital, his cardiac monitor shows the lethal rhythm ventricular tachycardia.
When Diggle goes to find the building Maseo is hiding in, the blueprint appears on the screen the minute he touches it, without making any searches.
Just a few episodes prior, Diggle installs security doors at Verdant that were designed to keep out the League of Assassins, yet the police have no trouble entering when they come to arrest Oliver. Perhaps the secure features can be turned on and off during operating hours, but since Ra's and the League are in town and Lance had issued a very public arrest warrant this would seem an implausible choice.