Procedures for arresting suspected criminals in other countries after Brexit look positive, the National Crime Agency (NCA) has said.
New extradition, data sharing and law enforcement co-operation arrangements are underpinned by the European Convention on Human Rights.
Senior NCA official Steve Rodhouse said important provisions like the ability to arrest on an Interpol (international police) red notice have been preserved, along with timescales for the surrender of suspects.
He added: "The mechanics look positive.
"It is a new process, it is not well-practised, it is early days and we need to see how it operates.
"There is no reason why we cannot continue to have the same flexibilities and responsive system that the European Arrest Warrant gives us."
The warrant allows EU members to request the arrest and detention of criminals in other countries without extradition talks between them.
The Police Service of Northern Ireland (PSNI) and the Repubic of Ireland's An Garda Síochána have in the past made use of the procedure to extradite suspects between their jurisdictions.
A senior officer from the PSNI today said co-operation between the two services remains good after Brexit.
Mr Rodhouse is director-general of operations at the NCA, which is dubbed the British FBI and is an organisation focused on tackling organised criminals.
He told a virtual meeting of MPs on the Northern Ireland Affairs Committee that criminal gangs are always on the alert for new opportunities.
"Organised criminals are creative, agile, responsive and are always looking to exploit some part of our system for their gain and for others' misery," he said.
"I am very confident in the ability of the NCA and our partner agencies to keep pace with that and get ahead of it, but it keeps people up 24 hours a day doing that work and we have to continue to do so."
The end of the transition period has created significant new work for the UK's Border Force in Northern Ireland, which up to now was focused on the relatively small number of travellers from outside the EU arriving directly into the country.
It has scaled up its number of employees by 50% - to 150 - and plans to recruit more.
Paul Morgan, a senior director at the organisation, said it is always alert to new risks and threats and will continue to monitor those.
