The police retain primacy and are the lead in the event of a terrorist attack on British soil, but the military will provide support if requested. If a situation is deemed to be outside the capabilities of police firearms units (such as a requirement for specialist breaching capabilities), the SAS will be called in under the Military Aid to the Civil Authorities legislation. Additionally, some categories of operation-such as the recapture of hijacked airlines or cruise ships, or the recovery of nuclear or radioactive IEDs remain a military responsibility.