The Provisional IRA still exists but is not engaged in terrorism, Northern Ireland's senior police officer said.
Individual members cooperated in shooting dead Kevin McGuigan in East Belfast but there is no evidence the killing was sanctioned by the organisation, Police Service of Northern Ireland (PSNI) chief constable George Hamilton said.
Some structures from the 1990s remain in place although their purpose has changed radically from violence to promoting peaceful, political republicanism, he said.
Mr Hamilton said: "They are not on a war footing, they are not involved in paramilitary activity in the sense that they were during part of the conflict."
Unionists have claimed Sinn Fein's credibility is in tatters and threatened to exclude the party from the devolved government at Stormont following the murder of Mr McGuigan as part of a suspected republican feud. Sinn Fein president Gerry Adams has said the IRA were not involved.
After years of ceasefire, the 1998 Good Friday Agreement and verified decommissioning of weapons republicans said in 2005 the IRA had gone "off the stage" and the British and Irish governments' independent monitoring commission found it had disbanded its terrorist infrastructure.
But the murder of the ex-IRA member and father-of-nine last week in the Short Strand by suspected members of the Provisional movement in cooperation with a group styling itself Action Against Drugs has threatened Stormont powersharing.
Mr Hamilton said in the organisational sense the Provisional IRA does not exist for paramilitary purposes.
"Nevertheless we assess that in common with the majority of Northern Ireland paramilitary groups from the period of the conflict, some of the PIRA structure from the 1990s remains broadly in place, although its purpose has radically changed since this period.
"Our assessment indicates that a primary focus of the Provisional IRA is now promoting a peaceful, political, republican agenda.
"It is our assessment that the PIRA is committed to following a political path and is no longer engaged in terrorism.
"I accept the bona fides of the Sinn Fein leadership regarding their rejection of violence and pursuit of the peace process and I accept their assurance that they want to support police in bringing those responsible to justice.
"We have no information to suggest that violence, as seen in the murder of Kevin McGuigan, was sanctioned or directed at a senior level in the republican movement."
He said some current and former PIRA members continued to engage in criminal activity and occasional violence for "personal gain or personal agendas".
Mr Hamilton added: "They are little more than an organised crime group in my view and we assess that Action Against Drugs is an independent group that is not part of or a cover name for the PIRA."