I don't really follow drafts that often, so there are a couple things that aren't that clear to me.
First off, what does it mean for a player to still have a year of eligibility left?
And secondly, why is preference given to the NFL? You hears these guys talking about drafting players but maybe having to wait a little longer because of the NFL. If a team drafts a player, should that team have the "rights" to him?
The CFL draftworks more like the NHL draft than the NFL draft in this regard. In the CFL, players may reach draft eligibility before completion of their college tenure, so it is possible to get drafted, yet still return to your college to play (assuming you've not already exhausted your collegge eligibility years). Think like hockey where 18 year olds are eligible for the draft, and are picked, yet many return to their junior teams to play. In the NFL (and NBA), you have to end your collegiate career to be eligible for the draft.
The CFL draft only grants the selecting team that player's rights for play in the CFL. Neither the CFL nor the NFL has the ability to restrict that player's rights in another league. It is not uncommon for a player's rights to be owned by a team in each league. As for why preference is given to the NFL - that's a matter of money.
Canadian players are elgible for the draft fours years after they enter college. Many of the Canadians going down to the NCAA don't play their first year (they call it red shirting them) so they still have four years of elgibility left and they are really there a total of for five years.
The CFL drafts them after they have been in College for four years, but its really only some of their Junior years as far as the NCAA is concerned. The NFL goes by NCAA Seniors unless the player declares himself as coming out early.
Players like Keith Shologan and Jesse Newman played right away so were only in College four years. Other players such as Justin Sorenson and Andrew Woodruff were red shirted their first year so have another year of College elgibility.