Can a Canadian citizen enter USA with an Impaired Driving conviction 
(DWI, DUI)? for the purposes of:
transit thru on connecting flight
visit for business or pleasure
work
live as permanent resident to seek USA citizenship

Under Canadian Law all criminal charges are "federal offences".
Impaired driving as its known in Canada is a criminal offence.
the American equivalent would be Drive Under Influence (DUI)
or DWI.
A hopefully current CCC is cited here:

http://www.lawyers.ca/statutes/criminal_code_of_canada_impaired_driving.htm

For the first offence the minimum penalty for a Canadian Law
conviction is a $600 fine.

Hello.

First of all, I must note that Google Answers provides general
information. It is not intended as, and should not be taken as,
professional legal advice. This answer is not a definitive statement
of the law.  This answer should in NO WAY be relied upon as the basis
for anyone's decision to enter the United States. If you need
professional legal advice, you should contact a qualified immigration
attorney.
--------------------

The federal law concerning inadmissibility of aliens into the U.S. is codified at:
8 United States Code § 1182- Inadmissible aliens
http://www4.law.cornell.edu/uscode/8/1182.html

Here is the pertinent part of the code:

Sec. 1182. - Inadmissible aliens
(a) Classes of aliens ineligible for visas or admission
Except as otherwise provided in this chapter, aliens who are
inadmissible under the following paragraphs are ineligible to receive
visas and ineligible to be admitted to the United States:
....
2) Criminal and related grounds
(A) Conviction of certain crimes
(i) In general
Except as provided in clause (ii), any alien convicted of, or who
admits having committed, or who admits committing acts which
constitute the essential elements of -
(I)
a crime involving moral turpitude (other than a purely political
offense) or an attempt or conspiracy to commit such a crime, or
(II)
a violation of (or a conspiracy or attempt to violate) any law or
regulation of a State, the United States, or a foreign country
relating to a controlled substance (as defined in section 802 of title
21), is inadmissible."
source:
8 United States Code § 1182- Inadmissible aliens
http://www4.law.cornell.edu/uscode/8/1182.html


Now, is a basic DWI/DUI a "crime involving moral turpitude"?

"The BIA [Board of Immigration Appeals] has unequivocally determined,
however, that simple DUI convictions, even if repeated, are not crimes
of moral turpitude. In re Torres-Varela, 23 I. & N. Dec. 78, Int. Dec.
3449 (B.I.A. 2001) (en banc)."
source:
SALMERON v. INS (2003), UNITED STATES COURT OF APPEALS, FOR THE NINTH CIRCUIT
http://www.ca9.uscourts.gov/ca9/newopinions.nsf/65A98770E13FD80488256D13006CA3F2/$file/0270704.pdf?openelement


Also see: GROUNDS OF DEPORTABILITY AND INADMISSIBILITY RELATED TO CRIMES:

"5.  Driving Under the Influence Offenses
            A conviction for driving under the influence (DUI) is not
a crime involving moral turpitude.  Matter of Lopez-Meza, 22 I&N Dec.
1188 (BIA 1999).  Since a second DUI offense does not change the
character of the offense, it does not involve turpitude.  Matter of
Torres-Varela, 23 I&N Dec. 78 (BIA 2001).  Nevertheless, the BIA has
held that a noncitizen conviction for driving under the influence
involved moral turpitude when an element of the offense was that the
defendant knew or should have known that the authorities had revoked
his license.  Matter of Lopez-Meza, 22 I&N Dec. 1188 (BIA 1999)."
source:
GROUNDS OF DEPORTABILITY AND INADMISSIBILITY RELATED TO CRIMES, by the
nationalimmigrationproject.org
http://www.nationalimmigrationproject.org/crim%20mats%20june%202002.doc


Also see: "Drinking and Driving: Consequences of conviction" by Ron
Jourard (Toronto Lawyer)

"Criminal record
...A conviction also means you will have a criminal record which could
hurt your employment and restrict your ability to travel. However, it
should not prevent you from entering the United States as generally it
is not a crime of moral turpitude under U.S. immigration law.
 Travel to the United States
  If you are planning a trip to the U.S., as a precaution carry a
certified true copy of the information (court document) relating to
the conviction and a copy of the Criminal Code section under which you
were convicted.
  It would be wise also to have a letter from your doctor stating you
are not addicted to alcohol or drugs. If available, bring a certified
true transcript of the evidence underlying your conviction as well."
source: Ron Jourard
Criminal Lawyer, Toronto, Ontario
http://www.criminal-lawyer.on.ca/textversion-drinking-driving-1.html#TraveltoUS

Also see: 
"The Impact of Canadian Convictions on Admissibility to the United States"

"...he is admissible to the United States because driving under the
influence is not a crime of moral turpitude "
source: Heather Segal and Joel Guberman, Criminal Lawyers Association
http://www.criminallawyers.ca/newslett/19-4/segal.htm

Finally, your question mentioned various purposes of entry (e.g.,
connecting flight, business, pleasure, etc.).   The restrictions
imposed by § 1182 make no distinction concerning the circumstances or
purposes of entry. It's a blanket policy.

----------
search strategy:
"Criminal alien" inadmissible
"Criminal alien" inadmissible 1182
driving "moral turpitude" 1182
driving "moral turpitude" site:ca
driving "moral turpitude" "the united states" site:ca

I hope this helps.

Thanks Juggler. 
the last url (the Segal citation) describes a curious scenario.
The case of Mr. Smith (and G W Bush in 1976, R B Cheney 1962,1963) all
convicted of impaired (DWI stateside) would be admissable aliens into
the USA.

Thank you for the tip.
-juggler

This is very interesting as I have a friend, who received a DUI in MN
in 1991. Last year, while trying to go cross the MN/ON boarder,
Canadian border officials denied him entry into Canada because of this
conviction.....

Hmmmm, mabe its time I post a question about this.

Steph