The general limitations for a bachelors degree can be found in the University of Oregon Catalog. General limitation number 11 says Student may not receive credit for courses that are designated by the department as regressive prerequisites for courses in which they are currently enrolled or have already received credit.
Academic departments have designated the courses found in the links below as the courses that must be taken in a specified sequence in order to receive credit.
Look up a course you would like to take to see if you're eligible for credit:
Look up a course you've already taken to see which courses you're ineligible to earn credit for:
All of this information is available for download here: download CSV export file.