Douglas posts their Municipal Code on the Municode Web site, as many others do.
I don't find anything specifically allowing or disallowing bees, except for a table in the zoning section.
Title 16, Chap 4 - Zoning, section 7 - Use Standards: includes table 4-7 that lists allowed activities by zone. Beekeeping is specifically allowed in Zone "A" and "RR". The table notation states that empty cells in the table mean an activity is NOT allowed. As such, it seems beekeeping with in the city limits is restricted to Agriculture or Rural Residential zones.