I have the same issue:
<select size="1" name="Province">
<option value="" selected="selected">Choose</option>
<option value="AB">AB</option>
<option value="BC">BC</option>
<option value="MB">MB</option>
<option value="NB">NB</option>
<option value="NL">NL</option>
<option value="NS">NS</option>
<option value="NT">NT</option>
<option value="NU">NU</option>
<option value="ON">ON</option>
<option value="PE">PE</option>
<option value="QC">QC</option>
<option value="SK">SK</option>
<option value="YK">YK</option>
</select>
The form will validate even though a Province has not been selected.
I also tried a Regular Expression to no avail.