Police in Northern Ireland are ready for a no-deal Brexit, the chief constable has said.
Senior commanders have carried out detailed planning with other organisations in the country and across UK policing.
They tested officer numbers, equipment and planning scenarios, Simon Byrne added.
Powers like the European Arrest Warrant are part of decades of policing co-operation across both jurisdictions on the island which could fall away if the UK crashes out of the EU at the end of October.
The Police Service of Northern Ireland (PSNI) chief constable said: “Up to now I have seen no evidence to show that we are not match fit, but equally I am old enough in the tooth to know that no plan survives contact with the enemy, which is the old phrase from D-Day I think.
“As I sit here today I am really confident in the plans I have seen and went through yesterday.”
Mr Byrne is 10 weeks into his job as PSNI head.
His force faces a serious threat from dissident republicans opposed to the peace process.
Violent renegades could capitalise on any new customs infrastructure on the Irish border to attack police or members of the Army.
Mr Byrne said it is time for communities to tell dissidents enough is enough.
“The use of paramilitary attacks, beatings, breaking people’s legs, other limbs, in the name of the rule of law, is just odious,” he said.
“How anyone could think that is justified in a civil society is beyond me.”
He pledged to make dissidents’ lives a misery – even taking their children away from them.
“My message to them is – you carry on doing this, we will have your house, if you keep going we will have your car, we will have your kids, we will have your benefits and we will put you in jail.”
He said someone who has carried out a shooting is not fit to have custody of young children.
He added: “Why would I think you are safe in the presence of young children, so what safeguarding powers have we got to take your kids into care if that is a deterrent?
“I think we need to be more assertive, work with other agencies within the law to make people think twice before stepping into this space.”