During the Second Barons' War he switched sides twice, ending up in support of the king, for whose capture he was present at Lewes in 1264.

He opposed the initial baronial reform plan of May 1258, but along with other opponents capitulated and took the oath of the Provisions of Oxford.

By 1260, Warenne had joined the party of Simon de Montfort, but switched back to the king's side in 1263.

In 1282, Edward awarded him the Lordship of Bromfield and Yale in Wales, which was taken from Prince Gruffudd Fychan I and his son Madog Crypl.

The following spring saw the rebellion of William Wallace, Warenne was ordered to lead his army North by the king after initially refusing to return to Scotland.

The king himself took the field later that year, and Warenne was one of the commanders during the decisive English victory at the Battle of Falkirk.

[5] On 8 August, near the estuary of the Cree, Edward ordered his men and Warenne's to charge at a Scottish force—causing the Scots to flee.

Walter of Guisborough tells the story that the earl was served a writ of quo warranto ("by what warrant?")