A US Citizen receive a DWI offense in the state of New York in April
of the year 2000.  It remains on the driving record for 10 years. 
When would that US citizen be allowed to visit Canada because it is my
understanding that Canada does not allow any US Citizen to visit that
country.  I don't know what the time limit is before that citizen will
be allowed to visit without any problems crossing the boarder.

Hi conesuslk,

Driving while intoxicated is considered a felony in Canada and
therefore a person with a DWI conviction is not permitted to enter the
country. However, it is possible to be pardoned after five years have
passed since the sentence is completed by filing an Application for
Criminal Rehabilitation.  After ten years, filing the application is
not required.

Overcoming Criminal Inadmissibility
There are a number of ways to overcome a past conviction. For each of
them, you must provide the documentation and information concerning
the details of these convictions, including
    * information on the sentences you received for your convictions;
    * any pardons or discharges granted; and
    * information on the laws under which you were convicted or
pardoned or discharged.
Individual Rehabilitation
You can apply for individual rehabilitation if at least five years
have passed since you have completed all your criminal sentences.
To apply for individual rehabilitation, you must submit an application
and pay a processing fee.
Applications for rehabilitation can take over a year to process, so
make sure you plan for your visit far enough in advance.
Deemed Rehabilitation
You may be deemed rehabilitated if at least 10 years have passed since
you completed the sentence imposed for your crime. Some requirements
for deemed rehabilitation include:
    * You have only been convicted of one offence; and
    * The offence would be punishable in Canada by a maximum term of
imprisonment of less than 10 years.
You are not required to submit an application to be deemed rehabilitated.
http://www.cic.gc.ca/english/visit/conviction.html

Application for Criminal Rehabilitation
http://www.cic.gc.ca/english/applications/rehabil.html

Criminal Rehabilitation Guide
http://www.cic.gc.ca/english/pdf/kits/guides/5312E.PDF

Fees
http://www.cic.gc.ca/english/pdf/kits/forms/IMM5310B.PDF

I hope this helps. If you have any questions, please post a
clarification request and wait for me to respond before closing/rating
my answer.

Thank you,
hummer

I searched the Canada Border Services Agency (CBSA) website under
Visitors to Canada.