Originally Posted by Statutes and Statutory Construction, by Norman J. Singer
21:14 Conjunctive and disjunctive words
Where two or more requirements are provided in a section and it is in the legislative intent that all of the requirements must be fulfilled in order to comply with the statute, the conjunctive "and" should be used. Statutory phrases separated by the word "and" are usually interpreted in the conjunctive. Where a failure to comply with any requirement imposes liability, the disjunctive "or" should be used. Generally, courts presume that "or" is used disjunctively unless there is clear legislative intent to the contrary.
Originally Posted by MO Traffic Code
Every person operating a bicycle or motorized bicycle at less than the posted speed or slower than the flow of traffic upon a street or highway shall ride as near to the right side of the roadway as safe...
I think the confusion here is because meeting the "requirements" in this law means staying to the right. This is a restrictive law (not a real law term, I just made it up if you care) as opposed to a freeing law (again, my term). The freeing law in this case would read:
Every person operating a bicycle or motorized bicycle at (or greater than) the posted speed and faster than the flow of traffic upon a street or highway shall not be required to ride as near to the right side of the roadway as safe.
In this rephrasing of the law, I changed all of the negatives to positives and vice versa. It still reads the same way as HH and Noisebeam have been arguing and this new form fits nicer into the text quoted by Blue Order (which isn't saying what he thinks it's saying), specifically the bolded section. In this reversed version of the law, to be legally left, you must comply with both requirements. In the originally form, failure to comply with any requirement means riding to the right.