Is it possible to return after being deported? Yes it is. Need written permission
Here is somne information from the website of the Canadian Embassy in Washington, D.C.:
http://www.dfait-maeci.gc.ca/can-am/washington/visas/inadmissible-en.asp
TEMPORARY RESIDENT PERMIT, APPROVALS OF REHABILITATION, AND PERMISSION TO RETURN TO CANADA:
Those who have been convicted of an offence IN CANADA who wish to return to Canada must first apply for a PARDON from the CLEMENCY AND PARDONS DIVISION OF THE NATIONAL PAROLE BOARD. A Pardon permanently erases the Canadian criminal record, and any consequences of inadmissibility resulting from it. Those unable to obtain a pardon may still apply for a TEMPORARY RESIDENT PERMIT. For more information on pardons, contact:
NATIONAL PAROLE BOARD,
Clemency and Pardons Division,
340 Laurier Avenue West,
Ottawa, Ontario, Canada, K1A 0R1.
Those who have been convicted of an offence OUTSIDE CANADA, and have had 5 years elapse since the termination of the custodial portion (if any) of the sentence imposed (not the sentence served), may apply for a Minister's APPROVAL OF REHABILITATION. The Minister's Approval will permanently remove the inadmissibility caused by conviction.
If less than 5 years have elapsed, or if persons are only seeking entry to Canada for a single or limited period, then they may apply for a TEMPORARY RESIDENT PERMIT.
Those subject of a previous DEPORTATION ORDER FROM CANADA require PERMISSION TO RETURN TO CANADA before they can enter Canada. As well, those who have been subject of an EXCLUSION ORDER within the past 12 months require Permission to Return to Canada before they can re-enter Canada.