Here you go: http://law2.umkc.edu/faculty/projects/ftrials/riel/riel.html

The link you'll want in there is the "Treason Act & 6 Counts" which provides a transcript of the argument that indicated Riel violated the British Treason Act, which states:

""When a man do levy war against our Lord the King in his realm...or be adherent to the King's enemies in his realm, giving them aid and comfort in the realm and elsewhere, and thereof be proveably attainted of open deed by the people of their condition ... this shall be one ground upon which the party accused of the offence and legally proved to have committed the offence, shall be held to be guilty of the crime of high treason."

You might also find a copy of Riel's Defence: Perspectives on His Speeches, which has some good material. I don't know how it stacks up against other Riel reading, but I found that to be helpful in making the case for Riel's insanity defense.

The law2 site is an excellent encyclopedia of references. It contradicts itself some, has incomplete trial references omitting the NWMP, and omits Métis point of view.

Louis Riel was charged with High Treason as per the British Parliament 1352 Statute of Treason, the only allowable sentence upon guilty conviction was death, the judge had no choice.

Riel could have been charged with a lesser count of Treason-Felony, an 1800's statute passed after debate over death sentence, and which allowed the judge complete discretion in punishment upon guilty conviction.

But given Riel's history, specifically the Scott execution-assassination, and especially his direct insult to Mcdonald by surreptitiously showing up to Parliament, as a wanted man, and taking his seat in opposition across from the Prime Minister, and of course the war, all extremely hyperbolized in the press, the Prime Minister, attorney general, NWMP, and the judge had no option but to charge, try, convict and execute Riel for High Treason.

Riel's defense lawyers barely consulted with him, never informed him of their strategy of insanity plea, Riel actively faught this during his trial, never entered evidence of broken promises made over the Manitoba deal, never mentioned the expropriation-theft of homes and entire settlements.

A good source for this is Maggie Siggins' Riel: A Life of Revolution

You have to defend/prosecute Riel? He's already been prosecuted, the law2 source includes reference to 1985 Parliament Bill to exonerate him, so defend him. My own interpretation here, unsupported by literature: Prime Minister Mcdonald was adamant the American Indian wars would not be imported to Canada, it was the raison d'etre for creating the NWMP, one Métis-Indian war won, so of course a final answer was required, simply Mcdonald was scared of Louis Riel. With not too much effort Riel established a new province, he was given audiences by the US President Grant who invited him to become a US citizen, and several Indian tribes banded together to ask Riel to lead them in a solution against Canadian government intransigence. Mcdonald needed this force to go away for good.