We know that Edward IV made the Duke of Gloucester Constable of England for life in 1471, when he was restored but deprived of the services of John Tiptoft (Earl of Worcester) and Richard, Earl Rivers, both of whom had been executed during the Warwick-Lancastrian revolt. So he was definitely Constable in the aftermath of Edward’s death. He was definitely Lord Protector of the Realm as well – we know this because none of his adversaries sought to prevent him from taking the post, even though the Human Shredder managed to destroy Edward’s codicil that appointed him.
Now here is the 1351 law on treason:
Note that it includes the Lord Protector as from 1459, when the Duke of York was appointed to that position. Henry VI’s council set an important precedent by defining offences against the Protector as treason in the same way that those offences against the King would be.
Now here are the powers Edward granted to Rivers in 1469:
Will someone tell me if I am going too quickly for those slow on the uptake in Alexandria?