The CBC reports that Grewal is not seeking re-election.
More to follow.
Update. Public Eye Online discusses rumours about potential Conservative candidates in the riding.
Update 2. CTV News adds comments of Harper ("I think he's done what's in the interests of the party by deciding not to run.") and their Ottawa bureau chief suggests that Conservatives "encouraged him to leave".
The CBC quotes John Reynolds as saying that the Conservatives had not pressured Grewal into resigning.